Bulugh al-Maram #703

Sulaiman bin Buraidah narrated on the authority of his father (RAA) that the Prophet (ﷺ) taught us that when we visit graves we should say, “Peace be upon you, O believing men and women, O dwellers of this place. Certainly, Allah willing, we will join you. We supplicate to Allah to grant us and you well being.” Related by Muslim.