Musannaf Ibn Abi Shaybah

Hazrat Ali (may Allah be pleased with him) says that whoever joins the Imam for two rak'ahs should recite (Qira'at) in those rak'ahs which he has caught.

Hazrat Umar bin Khattab and Hazrat Abu Darda used to say that whatever part of the prayer you join with the Imam, consider it as the first part of your own prayer.

Hazrat Umar bin Abdul Aziz says: Make it the first part of your prayer.

Hazrat Saeed and Hasan say that whichever part of the prayer you join with the Imam, consider it as the first part of your own prayer.

The same is narrated from Hazrat Ali (may Allah be pleased with him).

Hazrat Saeed bin Jubair says that whatever part of the prayer one catches, he should recite in it. Because Hazrat Saeed bin Jubair believed in reciting quietly behind the Imam.

Hazrat Ali (may Allah be pleased with him), regarding the person who misses one or two rak'ahs with the Imam, says that he should recite during the Imam's pause. Hasan also says the same.