Jami` at-Tirmidhi 1054
جامع الترمذي#1054SahihSulaiman bin Buraidah narrated from his father that:The Messenger of Allah said: "I had prohibited you from visiting the graves. But Muhammad was permitted to visit the grave of his mother: so visit them, for they will remind you of the Hereafter
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 Muslim
In-book reference: 10:90