Does prostrating or bowing by way of greeting come under the heading of shirk?
Question

I read on a website that prostrating to anyone other than Allah, if it is done by way of greeting, constitutes disbelief and shirk, because prostration is an act of worship and it is not permissible to direct it towards anyone other than Allah. Is this correct?
Praise be to Allah.Firstly: 
Prostration – and also bowing – is of two types: 
1. Prostration by way of worship
This type of prostration is done by way of expressing humility, submission and worship, and cannot be done for anyone except Allah, may He be glorified and exalted. Whoever prostrates to anyone other than Allah by way of worship has committed an act of major shirk.
2. Prostration by way of greeting
This is done by way of greeting, showing respect and honouring the person to whom the prostration is done. This kind of prostration was permissible in some of the laws revealed to Prophets before Islam, but then Islam prohibited and forbade it. So whoever prostrates to any created being by way of greeting has done a prohibited act, but he has not fallen into shirk or disbelief. 
Shaykh al-Islam Ibn Taymiyah said:
Prostration is of two types: prostration by way of pure worship, and prostration by way of honouring and showing respect. As for the former, it can only be done for Allah.
End quote in Majmoo‘ al-Fataawa (4/361) 
And he said: The Muslims are unanimously agreed that prostration to anyone other than Allah is prohibited.
End quote from Majmoo‘ al-Fataawa (4/358) 
And he said:
The texts of the Sunnah and the consensus of the ummah indicate that it is prohibited to prostrate to anyone other than Allah according to the law brought by our Prophet (blessings and peace of Allah be upon him), whether by way of greeting or worship, as the Prophet (blessings and peace of Allah be upon him) forbade Mu‘aadh ibn Jabal to prostrate to him when he came from Syrian and prostrated to him by way of greeting. 
End quote from Jaami‘ al-Masaa’il (1/25) 
Al-Qurtubi said:
With regard to this prostration that is prohibited, the ignorant extreme Sufis have taken it as a custom in their gatherings (when they begin their dhikr and nasheeds), and when they enter upon their shaykhs and pray for forgiveness. So you see one of them, when he is overcome with ecstasy – as they claim – prostrating by putting his forehead to the ground, because of his ignorance, whether he is facing towards the qiblah or otherwise,  out of ignorance on his part. May they be doomed! 
End quote from Tafseer al-Qurtubi (1/294) 
Secondly: 
With regard to the view that prostration to anything other than Allah is shirk in all cases, because prostration in and of itself is an act of worship that cannot be directed to anyone other than Allah, this is a weak view. This is indicated by the following: 
1.
Allah commanded the angels to prostrate to Adam; if merely prostrating was shirk, Allah would not have commanded them to do that. 
At-Tabari said: “…then fall (you) down prostrating yourselves unto him” [al-Hijr 15:29] – this refers to the prostration of greeting and honour, not the prostration of worship. 
Ibn al-‘Arabi said: The ummah is unanimously agreed that the angels’ prostration to Adam was not a prostration of worship. 
End quote from Ahkaam al-Qur’an (1/27) 
Ibn Hazm az-Zaahiri said: There is no difference of opinion among any of the Muslims that their prostration to Allah, may He be exalted, was a prostration of worship, and their prostration to Adam was a prostration of greeting and respect.
End quote from al-Fasl fi’l-Milal wa’l-Ahwa’ wa’n-Nihal (2/129).
2.
Allah has told us about the prostration of Ya‘qoob and his sons to Yoosuf (peace be upon him). If it were shirk, the Prophets of Allah would not have done it. 
We cannot say that this was part of the religious teachings of those who came before us, because shirk has never been permitted in the teachings of any of the Prophets at all, and the teachings and symbols of Tawheed (affirmation of the oneness of Allah) have not changed from the time of Adam until the time of our Prophet Muhammad (blessings and peace of Allah be upon him). 
At-Tabari said: Ibn Zayd said concerning the verse, “and they fell down before him prostrate” [Yoosuf 12:100]:
That was a prostration by way of honouring and showing respect, as the angels prostrated to Adam by way of honouring and showing respect; it was not a prostration of worship. 
Rather with regard to the one who said that their prostration was a greeting among them, what he meant was that it was a custom on their part and was not by way of worshipping one another, and what may support this view is the fact that this custom continued to be practised by people for a long time, and was not done by way of worshipping one another. 
End quote from Jaami‘ al-Bayaan (13/356) 
Ibn Katheer said:
This was allowed in their laws and teachings: when they greeted an elder, they would prostrate to him. This remained permissible from the time of Adam until the teachings of ‘Eesa (peace be upon him), but this is prohibited for this ummah, and prostration is only for the Lord, may He be glorified and exalted.
End quote from Tafseer al-Qur’an al-‘Azeem (4/412) 
Al-Qaasimi said:
What there can be no doubt about is that it was not a prostration of worship or humility; rather it was a prostration of respect only, beyond a doubt.
End quote from Mahaasin at-Ta’weel (6/250) 
3.
Mu‘aadh prostrated to the Prophet (blessings and peace of Allah be upon him) when he returned from Syria. If it were shirk, the Prophet (blessings and peace of Allah be upon him) would have explained that to him, but the most that happened in that regard was that he explained to him that it was not permissible to prostrate to him. 
It was narrated that ‘Abdullah ibn Abi Awfa said: when Mu‘aadh ibn Jabal came from Syria, he prostrated to the Prophet (blessings and peace of Allah be upon him, who said, “What is this, O Mu‘aadh?” He said, I went to Syria and saw them prostrating to their archbishops and patriarchs, and I wanted to do that for you. The Messenger of Allah (blessings and peace of Allah be upon him ) said, “Do not do that. If I were to command anyone to prostrate to anyone other than Allah, I would have commanded women to prostrate to their husbands. By the One in Whose hand is the soul of Muhammad, no woman can fulfil her duty towards Allah until she fulfils her duty towards her husband.”
Narrated by Ibn Maajah (1853); classed as hasan by al-Albaani 
Shaykh al-Islam said: It is well known that he did not say: If I were to command anyone to be worshipped.
End quote from Majmoo‘ al-Fataawa (4/360) 
Adh-Dhahabi said:
Do you not see that the Sahaabah, in their great love for the Prophet (blessings and peace of Allah be upon him), said: Shouldn’t we prostrate to you? And he said no. If he had given them permission, they would have prostrated to him by way of honouring and showing respect, not by way of worship, as the brothers of Yoosuf (peace be upon him) prostrated to Yoosuf. 
Something similar may be said about the Muslim prostrating to the grave of the Prophet (blessings and peace of Allah be upon him) by way of veneration and respect: he does not commit an act of disbelief thereby; rather he is sinning. So he should be told that this is not allowed, and the same applies to praying facing towards the grave. 
End quote from Mu‘jam ash-Shuyookh al-Kabeer (1/73). 
4.
It is proven in some hadiths that some animals prostrated to the Prophet (blessings and peace of Allah be upon him). If merely prostrating constituted shirk, this would not have happened in the case of the Prophet (blessings and peace of Allah be upon him). 
Shaykh al-Islam said:
Animals used to prostrate to the Prophet (blessings and peace of Allah be upon him), and animals do not worship any but Allah, so how can it be said that prostrating to something implies worship thereof?
End quote from Majmoo‘ al-Fataawa (4/360) 
5.
“Mere prostration” is one of the shar‘i rulings which may change from one set of laws to another, unlike matters of Tawheed which is to be established in the heart; it is fixed and does not change. 
Shaykh al-Islam said:
With regard to humility and devotion in the heart, acknowledgement of Lordship and servitude, this can never be to anyone except Allah alone, may He be glorified and exalted, and if directed towards anyone other than Him, it is prohibited and invalid. 
As for prostration, it is something that has to do with laws and decrees, because Allah, may He be exalted, has commanded us to prostrate to Him. If He had commanded us to prostrate to any of His creation other than Him, we would have prostrated to that other one, in obedience to Allah, may He be glorified and exalted, if He wanted us to venerate the one to whom we prostrated. If He had not obliged us to prostrate, it would not be obligatory to do it at all. 
The angels’ prostration to Adam was an act of worship to Allah, in obedience to Him and as a means of drawing closer to Him. For Adam it was an honour and a token of respect. 
The prostration of the brothers of Yoosuf to him was a form of greeting. Do you not see that if Yoosuf prostrated to his parents by way of greeting, that would not be makrooh (disliked).
End quote from Majmoo‘ al-Fataawa (4/360) 
6.
Differentiating between prostration by way of greeting and prostration by way of worship is the view of the majority of scholars of different madhhabs. 
Fakhr ad-Deen az-Zayla‘i said:
What they do of kissing the ground before the scholars is haraam, and the one who does that and the one who approves of it are sinning, because it resembles idol worship. 
As-Sadr ash-Shaheed stated that he does not become a disbeliever by doing this prostration, because what he intends thereby is a greeting.
End uqote from Tabyeen al-Haqaa’iq (6/25) 
Ibn Nujaym al-Hanafi said: Prostration to tyrants constitutes disbelief, if what is intended thereby is worship, but not if what is intended thereby is a greeting, according to the view of the majority.
End quote from al-Bahr ar-Raa’iq (5/134). 
An-Nawawi said:
What many of the ignorant do of prostrating before shaykhs is definitely haraam, in all cases, whether it is facing towards the qiblah or otherwise, and whether the intention is to prostrate to Allah, may He be exalted, or it is done out of heedlessness. In some cases it constitutes disbelief or almost does. May Allah, the Most Generous, pardon us. 
End quote from al-Majmoo‘ Sharh al-Muhadhdhab (4/69) 
Shihaab ad-Deen ar-Ramli said: 
Merely prostrating before the shaykhs does not mean that venerating the shaykh is like venerating Allah, may He be glorified and exalted, in the sense that he is worshipped. It only constitutes disbelief if that is the intention. 
End quote from Nihaayat al-Muhtaaj ila Sharh al- Minhaaj (1/122)
Ar-Ruhaybaani said:
Prostrating to rulers or the dead with the intention of worship constitutes disbelief, and this is agreed upon unanimously by the Muslims. Greeting a human being by prostrating to him is a grave major sin.
End quote from Mataalib Ooli an-Nuha (6/278) 
Ash-Shawkaani said:
It is essential to clarify this by noting that if this prostration is done with the intention of affirming the Lordship of the one to whom one prostrates, then by prostrating in this manner he has ascribed a partner to Allah, may He be glorified and exalted, and affirmed that there is another god with Him. 
But if his intention is only to show respect, as happens often with those who enter upon foreign (non-Arab) kings, where they kiss the ground in veneration of the king, this does not constitute disbelief at all. All scholars are agreed that labelling a specific person as a disbeliever is a very serious matter and is not to be taken lightly. 
End quote from as-Sayl al-Jaraar (4/580) 
Shaykh Muhammad ibn Ibraaheem said:
Bowing when greeting is haraam, if the intention is to greet the person. If it is intended by way of worship, then it constitutes disbelief. 
End quote from Fataawa wa Rasaa’il ash-Shaykh Muhammad ibn Ibraaheem Aal ash-Shaykh (1/109) 
Shaykh ‘Abd al-‘Azeez ‘Abd al-Lateef said:
it is well-known that prostration by way of worship, which is based on humility, submission and veneration to Allah alone, is part of Tawheed (affirmation of the Oneness of Allah), to which all the Messengers called. If it is directed to anyone other than Allah, then it is shirk and ascription of rivals to Allah. 
But if a person prostrates to his father or a scholar and the like, and his intention is to offer a greeting and show respect, then this comes under the heading of prohibited matters that are less than shirk. But if the intention is to show submission and humility, then this constitutes shirk. 
End quote from Nawaaqid al-Eemaan al-Qawliyyah wa’l-‘Amaliyyah (p. 278) 
See also the answer to question no. 8492
 And Allah knows best.