Riyad as-Salihin, Book 1, Hadith 313 (In-Book)

Abu Hurairah (May Allah be pleased with him) reported: Messenger of Allah said, "No son can repay (the kindness shown by his father) unless he finds him a slave and buys him and emancipates him".[Muslim].

عَنْ أَبِي هُرَيْرَةَ رضي الله عنه، قَالَ: قَالَ رَسُولُ الله صلى الله عليه وسلم ‏ "‏لاَ يَجْزِي وَلَدٌ وَالِدًا إِلاَّ أَنْ يَجِدَهُ مَمْلُوكًا فَيَشْتَرِيَهُ فَيُعْتِقَهُ‏" ‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏

sunnah.com