Nafi' narrates from Ibn Umar (may Allah be pleased with them both) that when the Messenger of Allah (peace and blessings be upon him) drew near the minbar on Friday, he would greet those sitting near it with salam; then, when he ascended the minbar, he would turn towards the people and give the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5742