ذِكْرُ خَبَرٍ ثَانٍ يُصَرِّحُ بِصِحَّةِ مَا ذَكَرْنَاهُ
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. (Using translation from Muslim 954a)
أَنَّ النَّبِيَّ ﷺ «صَلَّى عَلَى قَبْرٍ بَعْدَمَا دُفِنَ»