Sayyiduna Jabir bin Samurah (may Allah be pleased with him) said: I never saw the Messenger of Allah (peace and blessings be upon him) delivering the Friday sermon sitting; rather, he always delivered it standing. Whoever tells you that he (peace and blessings be upon him) delivered the sermon sitting, then call him a liar, for he (peace and blessings be upon him) did not do so. The Prophet (peace and blessings be upon him) would deliver the sermon, then sit, then stand and deliver the sermon (again); he (peace and blessings be upon him) used to deliver two sermons, sitting between them.
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1917