Sahih Bukhari Volume 3, Book 46, Hadith 2443

حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، أَنَّ سَالِمًا، أَخْبَرَهُ أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ ـ رضى الله عنهما ـ أَخْبَرَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ الْمُسْلِمُ أَخُو الْمُسْلِمِ، لاَ يَظْلِمُهُ وَلاَ يُسْلِمُهُ، وَمَنْ كَانَ فِي حَاجَةِ أَخِيهِ كَانَ اللَّهُ فِي حَاجَتِهِ، وَمَنْ فَرَّجَ عَنْ مُسْلِمٍ كُرْبَةً فَرَّجَ اللَّهُ عَنْهُ كُرْبَةً مِنْ كُرُبَاتِ يَوْمِ الْقِيَامَةِ، وَمَنْ سَتَرَ مُسْلِمًا سَتَرَهُ اللَّهُ يَوْمَ الْقِيَامَةِ ‏"‏‏.‏

Narrated By 'Abdullah bin Umar : Allah's Apostle said, "A Muslim is a brother of another Muslim, so he should not oppress him, nor should he hand him over to an oppressor. Whoever fulfilled the needs of his brother, Allah will fulfil his needs; whoever brought his (Muslim) brother out of a discomfort, Allah will bring him out of the discomforts of the Day of Resurrection, and whoever screened a Muslim, Allah will screen him on the Day of Resurrection."