Hadith 4:162
Sa'id b. al-Musayyib said he prayed behind Abu Huraira at the funeral of a boy who had never sinned and heard him say, “O God, protect him from the punishment in the grave.” Malik transmitted it.
وَعَنْ سَعِيدِ بْنِ الْمُسَيَّبِ قَالَ: صَلَّيْتُ وَرَاءَ أَبِي هُرَيْرَةَ عَلَى صَبِيٍّ لَمْ يَعْمَلْ خَطِيئَةً قَطُّ فَسَمِعْتُهُ يَقُولُ: اللَّهُمَّ أَعِذْهُ مِنْ عَذَابِ الْقَبْر. رَوَاهُ مَالك
Original Reference: Mishkat al-Masabih 1689