John Wesley on Genesis 34:18

Hamor and Shechem gave consent themselves to be circumcised. To this perhaps they were moved not only by the strong desire they had to bring about, this match, but by what they might have heard of the sacred and honourable intentions of this sign, in the family of Abraham, which it is probable they had some confused notions of, and of the promises confirmed by it; which made them the more desirous to incorporate with the family of Jacob.