When should the person who missed part of the prayer say the Takbir (Allahu Akbar)?
Chapter on the Two Eid Prayers
Al-Mughni
Book of Friday Prayer
Primary text
The person who missed part of the prayer should say the Takbir after completing the makeup portion (Qada') of what he missed. This is the stated position of Ahmad and the opinion of the majority of scholars. The reasoning is that this remembrance (Takbir) is legislated to occur after the Salam (conclusion of the prayer), thus it should not be performed in the middle of the prayer, similar to the second Salam or the supplication following the prayer.
Supporting text
Al-Hasan stated that the Takbir should be made before the makeup portion, arguing that since it is a remembrance legislated at the end of the prayer, the person joining late should perform it before the makeup, analogous to the Tashahhud. Mujahid and Makhul hold that the Takbir is said before the makeup, and then another Takbir is said after the makeup.