And in this is evidence that a gesture by the one praying, which people understand, does not invalidate or corrupt the prayer.

Sayyiduna Jabir (may Allah be pleased with him) narrates that the Messenger of Allah (peace be upon him) became ill, and we performed prayer behind him while he was leading the prayer sitting. When he turned towards us, he saw us standing, so he gestured to us (to sit), and thus we sat down.