The obligation of loving all Muslims
Abu Hamzah Anas bin Malik, radiyallahu 'anhu, who was the servant of the Messenger of Allah, sallallahu 'alayhi wasallam, reported that the Prophet, sallallahu 'alayhi wasallam, said:
"None of you truly believes (in Allah and in His religion) until he loves for his brother what he loves for himself"
[Al-Bukhari & Muslim]