From Sahih Bukhari (Hadith 4193):
Narrated Abu Raja:The freed slave of Abu Qilaba, who was with Abu Qilaba in Sham: `Umar bin `Abdul `Aziz consulted the people saying, "What do you think of Qasama." They said, "'It is a right (judgment) which Allah's Apostle and the Caliphs before you acted on." Abu Qilaba was behind `Umar's bed. 'Anbasa bin Sa`id said, But what about the narration concerning the people of `Uraina?" Abu Qilaba said, "Anas bin Malik narrated it to me," and then narrated the whole story
Reference: Bukhari 4193