首楞嚴義疏注經 2.22

2.22

Newly born is called an infant (hai); just beginning to walk is called a child (ru). Ru means tender and weak. Skin (fu) means spread, spread upon the surface. The fine lustrous pattern of the skin is called cou. These are all characteristics of the time of childhood. Reaching adulthood refers to when one becomes a grown man, from twenty and upward to the prime of strength; hence it says: "blood and qi were abundant and full." Declining years refers to his current age of sixty-two; his years are declining and decaying, nearing seventy, hence it says: "press upon old age and senility." Youth and old age being different, how could the World-Honoured One compare them?