原句应该是 When you saw only one set of footprints,it was then that I carried you.
当你看到（沙滩上）只有一双脚印的时候,那是那个时候我在抱着你.
这句话出自一个关于耶稣的故事...."Lord,you said that once I decided to follow you,you would walk with me all the way.But I have noticed that during the most troublesome times in my life,there is only one set of footprints.I don't understand why when I needed you most you would leave me." I replied,"My precious,precious child.I love you and I would never leave you.During your times of trial and suffering,when you see only one set of footprints,it was then that I carried you."