Al-Adab Al-Mufrad, Book 1, Hadith 36 (In-Book) ⓘ
Abu Hurayra said, "The dead person can be raised a degree after his death. He said, 'My Lord, how is this?' He was told, 'Your child can ask for forgiveness for you.'"
حَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، قَالَ: حَدَّثَنَا أَبُو بَكْرٍ، عَنْ عَاصِمٍ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ قَالَ: تُرْفَعُ لِلْمَيِّتِ بَعْدَ مَوْتِهِ دَرَجَتُهُ. فَيَقُولُ: أَيْ رَبِّ، أَيُّ شَيْءٍ هَذِهِ؟ فَيُقَالُ: وَلَدُكَ اسْتَغْفَرَ لَكَ.
also referenced under: Hadith 36 (Reference) & Book 1, Hadith 36 (English)