Q: Our imam recites surah sajdah on Friday’s. Sometimes we hear it as we enter the musjid but miss it. Same this can happen in taraweeh. We may be outside, hear them going doing in sajdah, what do we do? Do we just do a sajdah? What happens when we praying nalf and he read ayah of sajdah.
A: If you hear a verse of Sajdah while in prayer with the Imam, its fulfillment depends on your timing. If you join the Imam in the same Rakah the verse was recited and even though you did not do it with him, your Sajdah is considered fulfilled by the prayer of that Rakah itself, even if you missed the actual prostration within that Rakah. However, if you join the Imam after that Rakah has concluded, (in the next rakah) then you must perform the Sajdah Tilaawah independently after finishing your prayer.
By contrast, if you hear the verse from an outside source while you are performing a private prayer (like Nafl), you must not perform the Sajdah during your ‘private salah.’ Doing so would be an invalid addition to your prayer. Instead, simply complete your Salah first and then perform the sajdah separately afterward.
Allah Certainly Knows Best.