Answered by Ustadh Tabraze Azam
Question: In the scenarios below is the thana read: 1) Joined in 3rd rak’ah (imam is standing) of Asr? 2) joined in 3rd rak’ah of Isha (imam is standing)? 3) joined 1st rak’ah Asr late (imam is still standing)? 4) joined 1st rak’ah Isha imam is bowing?
Answer: Wa alaikum assalam wa rahmatullahi wa barakatuh,
I pray that you are in the best of health and faith, insha’Allah.
No, you would not recite the opening supplication (thana) in any of these scenarios.
When praying behind an imam you say the opening supplication (thana) wherever you join him in the prayer except if: [a] by doing so you will miss the cycle (rak`ah) or the prayer itself, or [b] he is reciting (aloud or silently).
[Haskafi, al-Durr al-Mukhtar; Ibn `Abidin, Radd al-Muhtar]
And Allah alone gives success.
Checked & Approved by Faraz Rabbani