Is it permissible, in Islamic law, to return a greeting by moving the right hand in a semicircular motion, then returning it over the left hand, during prayer?

The jurists have agreed that one should not return a greeting (salam) verbally during prayer. They differed, however, on returning it by gesture. The Hanafis held that one should not return it by gesture, while the Malikis deemed returning it by gesture obligatory. The Shafi'is considered returning it by gesture sunnah (recommended), whereas the Hanbalis considered it permissible.