Musannaf Ibn Abi Shayba 3:5737

Hushaym narrated to us, he said: Juwaybir informed us, from al-Dahhak, from al-Bara’, that Ali went out to al-Nakhla and prayed the Dhuhr and Asr [prayers] there as two rak'ahs each. Then he returned on the same day and said: "I wanted to teach you the Sunnah of your Prophet."