Musannaf Ibn Abi Shaybah 4849 — A man leading people in Zuhr and Asr

Jabir said: I asked Abu Ja'far, Salim, al-Qasim and Ata about a person who joins a congregation thinking it is the Zuhr prayer while they are praying Asr. They said: "After finishing he should pray Zuhr, and his Asr prayer is valid." He said: I asked Amir and Muslim bin Subayh about this, and they said: "When he has finished he should first pray Zuhr and then Asr, because Allah Almighty has ordained Zuhr before Asr; so that prayer does not count for him as Zuhr."