Sayyiduna Abu al-Darda (may Allah be pleased with him) narrates: We said: "O Messenger of Allah! When we meet (one another), which of us should be first to give the greeting of salam?" The Prophet (peace and blessings be upon him) said: "Whichever of you is more obedient to Allah Almighty."
Tabarani recorded it, and its chain contains narrators whom I do not know.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 12745