ENOfficial
Abu Hurayra reported that the Prophet, may Allah bless him and grant him peace, said, "A child cannot repay his father unless he finds him as a slave and the buys him and sets him free."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا قَبِيصَةُ، قَالَ: حَدَّثَنَا سُفْيَانُ، عَنْ سُهَيْلِ بْنِ أَبِي صَالِحٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ: لاَ يَجْزِي وَلَدٌ وَالِدَهُ، إِلاَّ أَنْ يَجِدَهُ مَمْلُوكًا فَيَشْتَرِيَهُ فَيُعْتِقَهُ.
sunnah.com