Neither shalt thou swear by thy head, because thou canst not make one hair white or black.
What is the connection between "thou canst not make one hair white or black" and "thou shalt not swear by thy head"?
I understand "your head" as a pars pro toto for the person’s body, as an injunction not to swear by your life (or, more broadly, the physical integrity of your body). I don’t understand in what sense the fact that you can’t change the color of one hair is related to that?
- The majority of human hair grows on the head. So the "thou canst not make one hair white or black" is an elegant stylistic device referring back to the head you are not to swear by.
- Obviously you can make your hair white or black by dying your hair. So "thou canst not make one hair white or black" is probably not to be understood literally.
- Hair turns increasingly white as people age. Maybe "thou canst not make one hair white or black" is to be understood as "some things are outside of your control"? But I am not sure how old people got some 2000 years ago, so "white hair = old" might not have been such a common connection to make at the time. And in some sense, you can make your hair white by just waiting and aging. So I am not sure if "thou canst not make one hair white or black" is to be interpreted as a symbol for unalterable facts such as aging?
- Maybe something got lost in translation? "Thou canst not make one hair white or black" might be idiomatic in some other language and has just been translated literally?