en_tn/pro/22/21.md

Have I not written for you ... you?

This rhetorical question can be translated as a statement. Alternate translation: "You need to know that I have written for you ... 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.