What is the ruling on trousers that show the shape of a man’s ‘awrah?
Question

What are the guidelines concerning T-shirts and trousers that show the shape of a man’s ‘awrah, especially when sitting?
Praise be to Allah.Firstly:
It is obligatory for the man to cover the area between the navel and the knees.
It is obligatory for the man to cover his ‘awrah, which is the area between the navel and the knees, except from his wife or concubine, because of the report narrated by at-Tirmidhi (2794), Abu Dawood (4017) and Ibn Maajah (1920) from Bahr ibn Hakeem, from his father, from his grandfather, who said: I said: O Prophet of Allah, with regard to our ‘awrah, what must we cover of it and what may we uncover? He said: “Cover your ‘awrah (completely) except from your wife and those whom your right hand possesses (i.e., concubines).” I said: O Messenger of Allah, what if the people are staying close together? He said: “If you can make sure that no one sees it, then do not let anyone see it.” I said: O Prophet of Allah, what if one of us is alone? He said: “Allah is more deserving that you should feel shy before Him than people.”
This hadith was classed as hasan by al-Albaani in Saheeh at-Tirmidhi.
And because the Prophet (blessings and peace of Allah be upon him) said: “The area between the navel and the knees is ‘awrah.” Narrated by at-Tabaraani, ad-Daaraqutni, Ahmad and Abu Dawood; classed as hasan by al-Albaani in Irwa’ al-Ghaleel, no. 271.
Ahmad (15927) narrated from Zur‘ah ibn Muslim ibn Jarhad that the Prophet (blessings and peace of Allah be upon him) saw Jarhad in the mosque, wearing a burdah (cloak) that left his thigh uncovered, so he said: “The thigh is ‘awrah.” Classed as hasan by the commentators on al-Musnad.
Ahmad (1849), Abu Dawood (3150) and Ibn Maajah (1460) narrated that ‘Ali said: The Messenger of Allah (blessings and peace of Allah be upon him) said to me: “Do not uncover your thigh and do not look at the thigh of anyone, living or dead.” The commentators on al-Musnad said: It is saheeh because of corroborating evidence; it was classed as saheeh by Ahmad Shaakir.
It was narrated that Abu Sa‘eed al-Khudri said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “No man should look at the ‘awrah of another man, and no woman should look at the ‘awrah of another woman.” Narrated by Muslim (338).
An-Nawawi (may Allah have mercy on him) said in Sharh Muslim:
The words of the Prophet (blessings and peace of Allah be upon him), “No man should look at the ‘awrah of another man, and no woman should look at the ‘awrah of another woman. No man should lie with another man under the same cover, and no woman should lie with another woman under the same cover,” indicate that it is prohibited for a man to look at the ‘awrah of another man or for a woman to look at the ‘awrah of another woman. There is no difference of scholarly opinion concerning that. Likewise, it is prohibited for a man to look at the ’awrah of a woman or for a woman to look at the ‘awrah of a man, according to scholarly consensus.
The wording of this hadith, which says that a man should not look at the ‘awrah of another man, implies that he should not look at the ‘awrah of  a woman, and it is more appropriate that that should be prohibited.
This prohibition applies to women other than wives and concubines. In the case of spouses, each of them may look at the ‘awrah of the other, with no restrictions. End quote.
Secondly:
Guidelines on covering the ‘awrah:
The ‘awrah is to be covered with that which does not show its colour or shape, because if either of these two can be discerned, then it is not covering and temptation could result from looking at it.
This condition is indicated by the report narrated by Ahmad (21786), ad-Diya’  al-Maqdisi in al-Ahaadeeth al-Mukhtaarah (1/441), and al-Bayhaqi from Usaamah ibn Zayd, who said: The Messenger of Allah (blessings and peace of Allah be upon him) gave me a thick Egyptian garment that Dihyah al-Kalbi had given him, and I gave it to my wife to wear. The Messenger of Allah (blessings and peace of Allah be upon him) said to me: Why are you not wearing the Egyptian garment? I said: O Messenger of Allah, I gave it to my wife to wear. The Messenger of Allah (blessings and peace of Allah be upon him) said to me: Tell her to wear something underneath it, for I fear that it may show the size of her bones.” Classed as hasan by al-Albaani in Jilbaab al-Mar’ah al-Muslimah (p. 131).
Al-Baaji (may Allah have mercy on him) said in al-Muntaqa Sharh al-Muwatta’ (7/224), explaining the meaning of the phrase “clothed yet naked”:
In al-‘Utaybah it is narrated from Ibn al-Qaasim that “naked” means: wearing clothes of thin fabric.
In my view, and Allah knows best, this word may have two meanings:
The first is that the fabric is thin, so it shows what is beneath it, and the eye can see what lies beneath it of beauty.
Or it may be that what is meant is a thin and light garment which does not cover the limb, in the sense that it shows the shape thereof.
Maalik (may Allah have mercy on him) said: I heard that ‘Umar ibn al-Khattaab (may Allah be pleased with him) forbade women to wear the qibaati [a type of Egyptian garment]. He said: Even though it is not see-through, it shows the shape.
Maalik said: that is, it clings to the body and shows the shape.
Maalik was asked about some young women wearing the qiba’ (a type of coat).
He said: I do not like that, because when they fasten this garment over their bodies, it shows their buttocks.
What is meant is that because it is so tight, it shows the shape of the limbs, buttocks and other parts that Allah has enjoined should be covered. And Allah knows best and is most wise in what He prescribes. End quote.
The guideline on showing the shape of the ‘awrah, which is prohibited, is that this refers to wearing tight garments that show the shape of the ‘awrah and the details of the limbs, buttocks, penis and thighs. Some of these trousers are so bad that it cannot be imagined that any wise person could wear them in front of men or women.
As for loose trousers that do not show that, there is nothing wrong with wearing them.
It says in Fataawa al-Lajnah ad-Daa’imah (3/430): The basic principle with regard to different types of clothing is that they are permissible, because they come under the heading of customs and traditions. Allah, may He be exalted, says (interpretation of the meaning):
{Say, “Who has forbidden the adornment of Allah which He has produced for His servants and the good [lawful] things of provision?” } [al-A‘raaf 7:32].
Excluded from that is whatever the religious texts indicate is prohibited (haraam) or disliked (makrooh), such as silk for men, and that which shows the shape of the ‘awrah, because it is thin and the colour of the skin beneath it can be seen, or because it is tight and shows the shape of the ‘awrah, because in that case it comes under the same ruling as if it were uncovered, and uncovering it is not permissible.
‘Abdullah ibn Qa‘ood, ‘Abdullah ibn Ghadyaan, ‘Abd ar-Razzaaq ‘Afeefi, ‘Abd al-‘Azeez ibn ‘Abdillah ibn Baaz. End quote.
In Fataawa al-Lajnah ad-Daa’imah (24/40) it says: The basic principle regarding clothes is that they are permissible, except that which is excluded by the religious texts at all times and in all situations, such as gold and silk for men, except in the case of scabies and the like; or wearing trousers that are not something worn exclusively by the disbelievers, but they are tight and show the shape of the limbs of the body and even the ‘awrah. That is not permitted.
But if the trousers are loose, then that is permissible, unless the intention in wearing them is to imitate those among the disbelievers who wear them.
The same applies to wearing a suit and necktie, which is not a kind of clothing that is worn exclusively by the disbelievers, so it is permissible, unless the intention of the one who wears it is to imitate them.
To sum up, the basic principle regarding clothing is that it is permissible, except that which the religious texts indicate is not allowed, as noted above.
‘Abdullah ibn Qa‘ood, ‘Abdullah ibn Ghadyaan, ‘Abd ar-Razzaaq ‘Afeefi, ‘Abd al-‘Azeez ibn ‘Abdillah ibn Baaz. End quote.
And Allah knows best.