Sayyiduna Buraydah (may Allah be pleased with him) narrates: "We came to the Prophet (peace and blessings be upon him) while he (peace and blessings be upon him) was praying, and he (peace and blessings be upon him) gestured to us with his hand to sit down."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1149