Sahih Muslim 2580
Salim reported on the authority of his father that Allah's Messenger (ﷺ) said:
A Muslim is the brother of a fellow-Muslim. He should neither commit oppression upon him nor ruin him, and he who meets the need of a brot'ier, Allah would meet big needs, and he who relieved a Muslim from hardship Allah would relieve him from the hardships to which he would be put on the Day of Resurrection, and he who did not expose (the follies of a Muslim) Allah would conceal his follies on the Day of Resurrection.
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، عَنْ عُقَيْلٍ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنْ أَبِيهِ،
 أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏
"‏ الْمُسْلِمُ أَخُو الْمُسْلِمِ لاَ يَظْلِمُهُ وَلاَ يُسْلِمُهُ مَنْ
 كَانَ فِي حَاجَةِ أَخِيهِ كَانَ اللَّهُ فِي حَاجَتِهِ وَمَنْ فَرَّجَ عَنْ مُسْلِمٍ كُرْبَةً فَرَّجَ اللَّهُ عَنْهُ بِهَا
 كُرْبَةً مِنْ كُرَبِ يَوْمِ الْقِيَامَةِ وَمَنْ سَتَرَ مُسْلِمًا سَتَرَهُ اللَّهُ يَوْمَ الْقِيَامَةِ ‏"‏ ‏.‏