From Sahih Muslim (Hadith 2211):
Sha'bi reported that the Messenger of Allah (ﷺ) observed prayer over a grave after the dead was buried and he recited four takbirs over him. Shaibani said:I said to Sha'bi: Who narrated it to you? He said: An authentic one, 'Abdullah b. 'Abbas. This is the word of a hasan hadith. In the narration of Ibn Numair (the words are): The Messenger of Allah (ﷺ) went to the grave which had been newly prepared and prayed over it, and they also prayed who were behind him and he recited four takbirs. I said to 'Amir: Who narrated it to you? He said: An authentic one who saw him, i e. Ibn 'Abbas
Reference: Muslim 2211