Musannaf Ibn Abi Shayba 3:2380

Abu Bakr narrated to us, he said: Shareek narrated to us, from Jabir, from 'Amir, and from al-Mughirah, from Ibrahim: They both said: If you are in the 'Asr prayer and you remember that you did not pray the Dhuhr, then withdraw, pray the Dhuhr, then pray the 'Asr.