Abu Umamah Sudaiy bin `Ajlan Al-Bahili (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "The person nearest to Allah is one who is the first to offer greeting."[Abu Dawud].The narration in At-Tirmidhi is: The Messenger of Allah (ﷺ) was asked: "O Messenger of Allah! When two persons meet, who should greet the other first?'' The Messenger of Allah (ﷺ) said, "The person nearest to Allah (i.e., one who is more obedient and therefore closer to Allah will say: As-Salam first."
App reference: Book 6, Hadith 14
Arabic/English book reference: Book 6, Hadith 858