# to teach you ... who sent you?

These words end the rhetorical question that began with the words "Have I not written" in Proverbs 22:20. It can be translated as a statement. "You need to know that I have written ... to teach you ... who sent you." (See: [[rc://en/ta/man/translate/figs-rquestion]])

# to those who sent you

This implies that the hearer is or will be one whom others send to gain and bring back information.