Genesis 34:15

But in this will we consent unto you: If ye will be as we be, that every male of you be circumcised;

Cross-reference

Genesis 34:22 shows the Shechemites accepting the circumcision condition — the fulfillment that the sons' demand in this verse set in motion.

Genesis 17:10 is God's covenant command to circumcise — the very sign Jacob's sons weaponize here as a deceptive condition for marriage.