What is the authenticity of the story in which a man asks a reciter of Surat Ghafir to supplicate to Allah with, "O Forgiver of sin, forgive me," and "O Accepter of repentance, accept my repentance," and "O Severe in punishment, pardon my punishment"?

Abu Nu'aym narrated in "Hilyat al-Awliya'" with a good chain of transmission from Thabit al-Bunani that while he was reciting Surat Ghafir, he heard a voice commanding him to say: "O Forgiver of sin, forgive me," and "O Acceptor of repentance, accept my repentance," and "O Severe in punishment, pardon my punishment." When he turned, he found no one. This narration is authentic from Thabit and is considered one of his miraculous deeds (karamat).