The Imaam stopped to Think after the surah Faatiha

Q: Salaah-509: Sometimes the Imaam stops to think before joining a Surah to the Surah Faatiha. Will this cause any deficiency to the salaah?

Answer: Apart from the time taken to say "Aameen" and to recite "Bismillaahir Rahmaanir Raheem?, if the Imaam pauses for a duration longer than it takes to recite "subhasnallaah" three times, sajdah Sahw will become binding. If the Sajdah Sahw is not made, the salaah will have to be repeated. If his pause was for a duration shorter than this. Sajdah Sahw will not be necessary. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2