Ibn 'Umar reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "A Muslim is the brother of another Muslim. He should not wrong him nor surrender him to his enemy. Allah will take care of the needs of anyone who takes care of the needs of his brother. On the Day of Rising Allah will dispel the anxiety of anyone who dispels the anxiety of another Muslim. On the Day of Rising Allah will veil anyone who veils another Muslim."

Riyadh-as-Saliheen by Imam Al-Nawawi, volume 2, hadith number 233 - Sunni Hadith