Is it obligatory to return the greeting of peace after completing an act of worship that prevents an immediate response, such as prayer and the Friday sermon, or is the obligation to return the greeting waived entirely?

It is permissible for a worshiper to return a greeting by gesturing, or preferably after finishing the prayer. As for someone who is greeted during the Friday sermon, the preponderant opinion is not to return the greeting, nor is he obligated to return it after the prayer ends, based on the saying of some scholars. Similarly, a person engaged in intercourse or relieving himself is not required to return the greeting.