Narrated by Abdullah bin Umar (Radhiallaho anho):
Allah’s Messenger (sallallaahu ‘alaihi wasallam) said,

“A Muslim is a  brother of another Muslim, so he should not oppress him, nor should  he hand himover to an oppressor. Whoever fulfilled the needs of his  brother, Allah will fulfill 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.”

Sahih Al-Bukhari Vol. 3 : No. 622