Jami` at-Tirmidhi 2723
جامع الترمذي#2723SahihNarrated Anas bin Malik:"When the Messenger of Allah (ﷺ) would give the Salam he would do so three times, and when he would say a statement, he would say it three times
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirHasan Sahih
Al-AlbaniHasan Sahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih Bukhari
In-book reference: 42:36