No son can repay the kindness of his father unless he finds him a slave and buys him and emancipates him. [Muslim]
«لاَ يَجْزِي ولدٌ والدًا إلا أن يجده مملوكًا، فَيَشْتَرِيَهُ فَيُعْتِقَهُ». [مسلم]