Musannaf Ibn Abi Shayba 10:130

Abu Bakr narrated to us, he said: ‘Abdah bin Sulayman narrated to us, from Yahya bin Sa’id, from Bukayr bin ‘Abd Allah bin al-Ashajj, from ‘Ata’ bin Yasar, who said: I was sitting with ‘Abd Allah bin ‘Amr when a man asked him about a man who divorced his virgin wife three times. ‘Ata’ said: I said, "The three [divorces] of a virgin are [counted as] one." ‘Abd Allah bin ‘Amr said: "What makes you know? You are only a judge and you are not a mufti. The one [divorce] makes it irrevocable, and the three [divorces] make her unlawful [for him] until she marries a husband other than him."