Whenever it was her night with the Messenger of Allah ﷺ, he would go out at the end of the night to al-Baqi and say, "Peace be upon you, abode of a believing people. What was promised to you tomorrow has come, and we, Allah willing, will follow you. O Allah, forgive the people of Baqi al-Gharqad."
أخبرنا علي بن حجر قال حدثنا إسمعيل قال حدثنا شريك وهو ابن أبي نمر عن عطاء
كان رسول الله ﷺ كلما كانت ليلتها من رسول الله ﷺ يخرج في آخر الليل إلى البقيع فيقول السلام عليكم دار قوم مؤمنين وإنا وإياكم متواعدون غدا أو مواكلون وإنا إن شاء الله بكم لاحقون اللهم اغفر لأهل بقيع الغرقد
Its takhrij, Muslim reported it in the chapter on visiting graves, in the chapter "What is said upon entering graveyards and the supplication for their inhabitants," hadith 974, from the hadith of Ismail bin Jafar through this same chain, and it is also found in Al-Kubra, hadith 2166.