It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that when the Negus (al-Najashi) died, the Prophet (peace and blessings be upon him) said: "Seek forgiveness for your brother." At this some people said: "He is ordering us to seek forgiveness for him, although he died in the land of Abyssinia?" So this verse was revealed: "And indeed, among the People of the Book are some who believe in Allah and in what has been revealed to you."
No one narrated this hadith from Hammad (may Allah have mercy on him) except Mu'ammal (may Allah have mercy on him).
Hadith Referenceالمعجم الأوسط / باب الألف / 2667
Hadith Takhrij«أخرجه الضياء المقدسي فى «الأحاديث المختارة» برقم: 1648، 2037، 2038، 2039، والنسائي فى «السنن الكبرى» برقم: 11022، 11023، والبزار فى «مسنده» برقم: 6555، 6556، والطبراني فى «الأوسط» برقم: 5147»