Musannaf Ibn Abi Shaybah

Hazrat Aamir and Ibrahim say that if you are performing the Asr prayer and you remember that you have not yet performed the Zuhr prayer, then break the prayer and first perform the Zuhr prayer, then the Asr prayer.

Ibrahim, regarding the person who forgets to perform the Zuhr prayer and remembers it at the time of Asr prayer, said that he should break the Asr prayer and first perform the Zuhr prayer, then perform the Asr prayer.

Hazrat Mughira states in his narration that if he remembers after offering the Asr prayer, then the Asr prayer is done; now he should offer the Zuhr prayer.

Hazrat Zuhri says that if a person remembers during the Asr prayer that he has not performed the Zuhr prayer, he should break this prayer and first perform the Zuhr prayer, then the Asr prayer.

Hazrat Sha’bah says that we asked Hazrat Hakam and Hazrat Hammad about a person who is performing one prayer and remembers another prayer. Both of them said that if he remembers before reciting Tashahhud or before sitting for the duration of Tashahhud, he should leave that prayer and first perform the other prayer, and if he remembers after Tashahhud, he should count that prayer and then return to the other prayer.