Du`a is worship
Question

What is the meaning of the hadith of the Prophet (blessings and peace of Allah be upon him): “Du`a’ is worship”?
Praise be to Allah.Firstly:
It was narrated from an-Nu‘maan ibn Basheer (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “Du`a is worship.” Then he recited the verse (interpretation of the meaning): “And your Lord says, ‘Call upon Me; I will respond to you.’ Indeed, those who disdain My worship will enter Hell [rendered] contemptible.” [Ghaafir 40:60]. Narrated by Ahmad in al-Musnad (18352) and al-Bukhaari in al-Adab al-Mufrad (714).
Du`a is of two types:

Du`a of asking, in which the individual asks Allah, may He be exalted, for that which will benefit him in this world and the hereafter, and to ward off that which would harm him in this world and the hereafter.
Du`a of worship, in which the individual is worshipping Allah, may He be exalted, by doing any kind of worship, in the heart, in his physical actions or in his financial actions.

At-Teebi said in Sharh al-Mishkaat: The grammatical structure of the sentence, in which the word al-‘ibaadah (worship) appears with the definite article al- is indicative of exclusivity, and that worship is nothing but Du`a [supplication]. End quote. (5/1708).
Ibn Rajab said in Fath al-Baari (1/20): You should understand that the original linguistic meaning of Du`a is to ask or seek, so it is asking for what the supplicant wants to get and prefers to attain. Sometimes it is the Du`a of asking of Allah, may He be glorified and exalted, and beseeching Him, such as when the person says “O Allah, forgive me; O Allah, have mercy on me.”  And sometimes Du`a is by taking appropriate measures by means of which one may attain what one wants, which is focusing on obeying and worshipping Allah, and remembering Him, and focusing on doing what He loves His slaves to do. This is the true essence of faith.
In Sunan al-Arba‘ah it is narrated from an-Nu‘maan ibn Basheer (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “Du`a is worship.” Then he recited the verse (interpretation of the meaning): “And your Lord says, ‘Call upon Me; I will respond to you.’ Indeed, those who disdain My worship will enter Hell [rendered] contemptible.” [Ghaafir 40:60].
There is no better means by virtue of which Allah grants a person what he likes and wards off what he dislikes than focusing on obeying Allah, worshipping Him and remembering Him. This is the essence of faith, and Allah wards off harm from those who have faith. End quote.
Secondly:
Usually the word Du`a, when mentioned in the verses of the Holy Qur’an, refers to both meanings, because they are interconnected. Everyone who asks of Allah verbally is worshipping Him, because Du`a is worship; when a worshipper prays to Allah, fasts or does Hajj, he is doing so by way of seeking reward from Allah, may He be exalted, and hoping to attain Paradise and be saved from punishment.
Shaykh ‘Abd ar-Rahmaan as-Sa‘di (may Allah have mercy on him) said:
Every time the Qur’an enjoins Du`a, and forbids calling upon anyone other than Allah, and praises those who call upon Allah in Du`a, that includes both the Du`a of asking and the Du`a of worship.
End quote from al-Qawaa‘id al-Hassaan (no. 51).
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said: Beseeching Allah and turning to Him and asking of Him by virtue of the righteous deeds that He has enjoined – such as the Du`a of the three who hid in the cave, who called upon Allah by virtue of their righteous deeds [as mentioned in the hadith], and beseeching Allah by virtue of the Du`a and intercession of the Prophets and the righteous – is something concerning which there is no dispute. In fact, it comes under the heading of the waseelah [means of nearness to Him] that Allah enjoined in the verses (interpretation of the meaning):
“O you who have believed, fear Allah and seek the means [of nearness] to Him”
[al-Maa’idah 5:35]
“Those whom they invoke seek means of access to their Lord, [striving as to] which of them would be nearest, and they hope for His mercy and fear His punishment”
[al-Israa’ 17:57].
Seeking means of nearness to Him is seeking to do acts of worship through which one may draw close to Him. In other words, one seeks to draw close to Him by means of that which may bring one closer to Him, may He be glorified, whether that is by means of doing acts of worship and obedience, and complying with His commands, or it is by means of asking of Him and seeking His protection, and turning to Him to bring benefit or ward off harm.
Du`a, in the Qur’an, includes both meanings, Du`a in the sense of worship and Du`a in the sense of asking. Even though each meaning implies the other, some calamity may befall a person, so he finds himself in a situation where he has to ask that his needs be met and that he be granted relief from his distress, so he seeks to achieve that by asking of Allah and beseeching Him. Although this is also worship and obedience, his initial aim is to attain what he is seeking of provision, help and well-being in general terms. Then his calling upon Allah in Du`a and beseeching Him is a means of increasing faith in Allah, may He be glorified and exalted, increasing knowledge of Him and love of Him, and finding joy in remembering Him and calling upon Him, which then becomes dearer to the individual and more important to him than the need that initially concerned him.
This is by Allah’s mercy towards His slaves: by means of worldly needs He drives them towards sublime religious goals.
A person may initially do what he is enjoined to do for the sake of worshipping Allah and obeying Him, and because of the love he has for Him and turning to Him in repentance, out of fear of Him and in compliance with His commands, even though that also leads to granting of provision, help and well-being. Allah, may He be exalted, says (interpretation of the meaning):
“And your Lord says, ‘Call upon Me; I will respond to you’”
[Ghaafir 40:40].
The Prophet (blessings and peace of Allah be upon him) said, according to the hadith that was narrated by the authors of as-Sunan, Abu Dawood and others: “Du`a is worship.” Then he recited the verse (interpretation of the meaning): “And your Lord says, ‘Call upon Me; I will respond to you.’ Indeed, those who disdain My worship will enter Hell [rendered] contemptible.” [Ghaafir 40:60].
This hadith may be understood, on the basis of Qur’an, as referring to both types of Du`a. “Call upon Me” means: worship Me and obey My commands; I will answer your Du`a. And it was said that it means: Ask of Me; I shall give to you. Both meanings are true.
End quote from Iqtidaa’ as-Siraat al-Mustaqeem (2/312-313).
For more information, please see the answer to question no. 113177.
And Allah knows best.