It is narrated from Hazrat Jabir (may Allah be pleased with him) that I have attended more than a hundred gatherings of the Prophet (peace and blessings be upon him). I always heard him delivering the sermon while standing; he would deliver the first sermon and then sit down, then stand up and deliver the second sermon.
Hadith Referenceمسند احمد / أول مسند البصريين / 20881
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف، شريك سيئ الحفظ لكنه توبع