In the folly of youth I one day shouted at my mother who then sat down with a grieved heart in a corner and said, weeping: ‘Hast thou forgotten thy infancy that thou art harsh towards me?’ 
 
        How sweetly said the old woman to her son   
        When she saw him overthrow a tiger, and elephant-bodied:   
       ‘If thou hadst remembered the time of thy infancy   
        How helpless thou wast in my arms   
        Thou would’st this day not have been harsh   
        For thou art a lion-like man, and I an old woman.’
Saadi Shirazi
http://www.poemhunter.com/poem/ch-06-on-weakness-and-old-age-story-06/