Musannaf Ibn Abi Shayba 3:3448

Abu Bakr narrated to us, he said: Abdullah ibn Idris narrated to us, from Hisham, from al-Hasan and Ibn Sirin, regarding the man who misses a rak'ah during the days of Tashriq. Ibn Sirin said: He performs the missed rak'ah, then he says the takbir. Al-Hasan said: He says the takbir, then he performs the missed rak'ah. Al-Hakam said: He says the takbir, then he performs the missed rak'ah.