Anas (May Allah be pleased with him) reported:
Whenever the Prophet ﷺ said something, he would repeat his words thrice so that the meanings would be understood fully; and whenever he came upon a group of people, he would greet them, and he would repeat salutation thrice.

[Al-Bukhari and Muslim].

عن أنس رضي الله عنه أن النبى ﷺ كان إذا تكلم بكلمة أعادها ثلاثاً حتى تفهم عنه، وإذا أتى على قومٍ فسلم عليهم سلم عليهم ثلاثاً. ((رواه البخاري)).