Question Summary:
Why some scholars says that pants and shirt wearing Haram? And whats rule of wearing cloths in islam?

Question Detail:

Why some scholars says that  pants and shirt wearing Haram? And whats rule of wearing cloths in islam?
(Kindly give answer in detail)

Answer :

In the name of Allah, Most Gracious, Most Merciful
Assalaamu `alaykum waRahmatullahi Wabarakatuh
Clothing is one of the greatest bounties of Allah Ta'ala. No person can do without it. Besides concealing the body, there are many other benefits in clothes. At times it presents the identity of a person, his country, nationality, religion, culture etc. Every group, nation, group takes pride in their clothing and are very serious and sensitive about it. Schools, colleges and institutes have their own distinctive dress codes. The police, army, doctors, nurses, postmen and some presidents have presidential uniform which represents their ideals. Islam, being a complete religion, has also given us a unique uniform.
Allah Ta'ala mentions in the Noble Quran:
يا بني آدم قد أنزلنا عليكم لباسا يواري سوآتكم وريشا ولباس التقوى ذلك خير ذلك من آيات الله لعلهم يذكرون

"O children of Adam! Verily We have sent down clothing for you
by means of which you cover your private organs
and a means of beatifications and clothes of piety, that is better"(al-A'raf 26)
 
In the above verse Allah Ta'ala explains three benefits of clothing. The first being to cover ones private parts. This is the chief objective of wearing clothes. It is also the distinguishing factor between human beings and animals. The fitra (nature) of human beings is to cover themselves. Revealing parts of ones body is a means of embarrassment. The first effort of shaitan was to cause Adam عليه السلام's body to be exposed. Today too, efforts are made to make people expose those parts of the body which ought to be covered. Covering oneself is the first obligation after Iman. This comes even before salah.
The second benefit of wearing clothes is that it is a means of beauty.
After mentioning the two aforementioned benefits, Allah Ta'ala mentions "and the clothes of piety, that is best"(7:26). In this part of the verse indication is made to the fact that the one should wear such clothes through which one gains the taqwa of Allah Ta'ala. One should not wear such clothes which are against the teachings of Islam eg. clothes revealing the shape of the body, men imitating women and vice versa, extravagant  clothes, clothes of fujjar and fussaq (open sinners) etc.
عن أم سلمة ، قالت : كان أحب الثياب إلى رسول الله صلى الله عليه وسلم القميص. «الشمائل للترمذي»
1.      Ummul Mu'mineem Sayyidatuna Salma رضي الله تعالى عنها reports that the kurta (long shirt) was the most beloved clothes to Nabi صلى الله عليه و سلم . (Shama'il of Tirmidhi).
2.      Nabi صلى الله عليه و سلم  also recommended the wearing of white clothes.
عن ابن عباس قال : قال رسول الله صلى الله عليه وسلم : عليكم بالبياض من الثياب ليلبسها أحياؤكم ، وكفنوا فيها موتاكم ، فإنها من خير ثيابكم.« الشمائل للترمذي»

Ibn Abbas رضي الله تعالى عنه narrates that Nabi صلى الله عليه و سلم  said: "Take to white clothes. Your living should wear it and shroud your dead in it as it is from the best of clothing." (Shama'il of Tirmidhi).
3.      Tying the turban was also from amongst the continues practice of Nabi صلى الله عليه و سلم  . Nabi صلى الله عليه و سلم  said:
 
عن ابن عمر رضي الله عنه : قال قال رسول الله صلى الله عليه و سلم : ( عليكم بالعمائم فإنها سيماء الملائكة وأرخوا لها خلف ظهوركم ) المعجم الكبير (12/383)
"Take upon yourselves the wearing of turbans as it is the sign of the angels and let it flow behind your shoulders." (Tabrani-Kabeer)
4.      As for women, they should wear such clothing which covers their entire body. Allah Ta'ala says in the Noble Quran:
يا أيها النبي قل لأزواجك وبناتك ونساء المؤمنين يدنين عليهن من جلابيبهن «الأحزاب 59»
"O messenger (صلى الله عليه و سلم ) say to Your wives, daughters and Muslim women to let down their jalabib (veils covering the entire body including the face).
قال الزهري وكانت هند لها أزرار في كميها بين أصابعها صحيح البخاري
5.      Zuhri رحمه الله تعالى narrates that Hind رضي الله تعالى عنها used to have buttons between her fingers. (Bukhari)
From this narration we can understand the hijab of the Sahabiyyat رضي الله تعالى عنهن.
Nabi صلى الله عليه و سلم mentions:
عن ابن عمر قال قال رسول الله -صلى الله عليه وسلم- « من تشبه بقوم فهو منهم ». سنن أبى داود
"Whoever imitates any nation then he is from amongst them."(Abu Dawood)
 
Explaining تشبه (imitating another nation) Maulana Ashraf Ali Thanwi رحمه الله تعالى mentions that if anything is a salient feature of a certain nation then adopting such ways would be considered as تشبه and would be impermissible to follow.
Keeping the above explanation in mind, when the British invaded India, wearing pants and shirt was considered to be their salient feature. Therefore the scholars of that time ruled wearing pants and shirt as impermissible. In today's time's, pants and shirt has become common and is no longer a feature of the British only. Therefore, though it cannot be ruled as impermissible, it is against the sunnah to wear such attire.
And Allah knows best
Wassalam
Ml. Ishaq E. Moosa,
Student Darul Iftaa
Checked and Approved by:
Mufti Ebrahim Desai
Darul Iftaa, Madrassah In'aamiyyah