اَلسَّلَامُ عَلَيْكُمْ أَهْلَ الدِّيَارِ مِنَ الْمُؤْمِنِيْنَ وَالْمُسْلِمِيْنَ إِنَّا إِنْ شَاءَ اللَّهُ بِكُمْ لَاحِقُوْنَ أَسْاَلُ اللَّهَ لَنَا وَلَكُمُ الْعَافِيَةَ

As-salamu 'alaykum ahlad diyari min al-mu'minina wal-muslimin, inna In sha' Allahu bikum lahikun, as-alullaha lana walakumul 'afiyah

Peace be upon you, the inhabitants of the grave, among the believers, and Muslims, and if Allah will then we shall join you. I pray to Allah peace for us and for you. Buraida ibnul husaib aslami (RA) narrated that the Messenger of Allah (ﷺ) used to teach them to recite this dua when anyone went to the graveyard.

Reference: Muslim: 975