Sayyiduna Jabir bin Samurah (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) used to deliver the Friday sermon standing, then sit, then stand and deliver the (second) sermon. Whoever tells you that he (peace and blessings be upon him) used to deliver the sermon sitting is lying. By Allah, I have prayed more than two thousand prayers with him (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5706