Musannaf Ibn Abi Shayba 34:274

Jarir narrated to us, from al-Shaybani, from al-Sha’bi, who said: Umar bargained with a man for a horse, so he rode it to test it, and it became injured. Umar said to the man, "Take your horse." The man said, "No." Umar said, "Appoint an arbiter between me and you." The man said, "Shurayh." So they sought judgment from him. Shurayh said, "O Commander of the Faithful, take what you purchased, or return it as you took it." Umar said, "Is judgment anything other than this?" He then appointed him to Kufa and sent him as a judge, for that was the first day he knew him.