Sahih Muslim Book 31, Hadith Number 6032.

Chapter : The merits of Ubayy b Ka’b and a group of Ansar (Allah be pleased with them).

Anas b. Malik reported that Allah’s Messenger (may peace be upon him) said to Ubayy b. Ka’b: I have been commanded to recite to you the Sura (al-Bayyinah) which opens with these words (Lam Yakunil-ladhiyna Kafaruu) He said: Has he mentioned to you my name? He said: Yes; thereupon he shed tears of joy. This hadith has been narrated on the authority of Anas through another chain of transmitters.