Sahih Muslim Book 4, Hadith Number 2126.

Chapter : What is to be said while visiting the graveyard and the supplication to be offered for the dead lying in the graves.

‘Aisha reported (that whenever it was her turn for Allah’s Messenger [may peace be upon him] to spend the night with her) he would go out towards the end of the night to al-Baqi’ and say: Peace be upon you, abode of a people who are believers. What you were promised would come to you tomorrow, you receiving it after some delay; and God willing we shall join you. O Allah, grant forgiveness to the inhabitants of Baqi’ al-Gharqad. Qutaiba did not mention his words: “would come to you”.