Jami` at-Tirmidhi 1932
جامع الترمذي#1932SahihAbu Ayyub Al-Ansari narrated that the Messenger of Allah said:: It is not lawful for the Muslim to shun his brother for more than three (days); they come fare to fare and this one turns away, and that one turns away. The best of them is the one who initiates the Salam
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 27:38