法苑珠林 50.12

50.12

又難報經云。左肩持父右肩持母。經歷千年便利背上。猶不能報父母之恩。

Furthermore, the Sūtra on the Difficulty of Repaying Parents' Kindness says: 'Even if one carried one's father on the left shoulder and one's mother on the right shoulder, passing through a thousand years while they relieve themselves upon one's back, one still could not repay the kindness of one's parents.'