Sayyiduna Jabir bin Samurah (may Allah be pleased with him) said: I had the opportunity to sit in the company of the Prophet (peace and blessings be upon him) a hundred times; he (peace and blessings be upon him) always delivered the sermon standing, and he would sit once (between the two sermons).
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1937