A Jewish woman mentioned punishment in the grave to Aisha, may Allah be pleased with her. Aisha asked the Messenger of Allah ﷺ about it, and he confirmed its reality. (Sahih al-Bukhari, Book of Funerals, chapter concerning punishment in the grave)
Aisha also reported that the Messenger of Allah ﷺ sought Allah's protection from the punishment of the grave in his prayers.
The report establishes both affirmation of grave punishment and supplication for protection from it.