Is it obligatory for the worshipper to return the greeting of Salaam during prayer?

If someone greets a person who is praying, whether they are an Imam or a follower, the praying person should not return the greeting verbally. If they do, their prayer becomes invalid according to the majority of scholars, due to the saying of the Messenger of Allah (peace be upon him): "Indeed, there is preoccupation in prayer."

As for returning the greeting by gesturing, it is permissible and is the view of the majority, and the Sunnah has validated it. The Prophet (peace be upon him) used to return the greetings of those who saluted him while he was praying by gesturing.

However, if the intention is to greet the Imam or those praying with him, the Shafi'is hold that one should intend to return their greeting.