The Book of Virtue, Good Manners and Joining of the Ties of Relationship (Kitab Al-Birr was-Salat-I-wa'l-Adab)
Muslim :: Book 32 : Hadith 6207
This hadith has been narrated on the authority of Zuhri with the same chain of transmitters with the addition of Ibn Uyaina (and the words are):" Do not cut off (mutual relations)."