SN 4.9 Paṭhamaāyu Sutta: Life Span
Mara says “Long is the life span of human beings. The good man should not disdain it. One should live like a milk-sucking baby. Death has not made it’s arrival.”
The Buddha replies “Short is the life span of human beings. The good man should disdain it. One should live like one with head aflame. There is no avoiding death’s arrival.”
I include this Sutta because it is the probably origin of the phrase often heard in Chan about practising as though one’s head were aflame.