Repaying kindess to parents

"If there were a person who carries his father on his left shoulder and his mother on his right shoulder until his bones were ground to powder by their weight as they bore through to the marrow, and if that person were to circumambulate Mount Sumeru for a hundred thousand kalpas until the blood that flowed out covered his ankles, that person would still not have repaid the deep kindness of his parents." ~ The Filial Piety Sutra

Source:
www.buddhanet.net/e-learning/filial-sutra.htm