It was narrated from Yazid bin Thabit that:
they went out with the Messenger of Allah one day and he saw a new grave. He said: What is this? They said: This is so-and-so, the freed slave woman of Banu so-and-so - whom Messenger of Allah knew - She died at midday and we did not like to wake you up when you were fasting and taking a nap. The Messenger of Allah stood (for prayer) and the people formed rows behind him. He said four Takbirs over her then he said: If anyone among you dies while I am still among you, inform me, for my prayer for his is a mercy.