Sahih Muslim Book 4, Hadith Number 2083.

Chapter : What is said in case of one who gets relief and the one from whom the other gets relief.

‘Imran b. Husain reported Allah’s Messenger (may peace be upon him) as saying: A brother of yours has died; so stand up and offer prayer for him, i.e. Negus. And in the Hadith transmitted by Zubair (the words are): “Your brother.”