Riyad as-Salihin

Ibn 'Umar (May Allah bepleased with them) reported: Messenger of Allah (ﷺ) said, "A Muslim is a brother of (another) Muslim, he neither wrongs him nor does hand him over to one who does him wrong. If anyone fulfills his brother's needs, Allah will fulfill his needs; if one relieves a Muslim of his troubles, Allah will relieve his troubles on the Day of Resurrection; and if anyone covers up a Muslim (his sins), Allah will cover him up (his sins) on the Resurrection Day".

[Al-Bukhari and Muslim].