It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: No child can repay the right of his father, except if he finds his father in a state of slavery and buys him and sets him free.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 9745