The imagery of cutting the foreskin of one’s heart and not hardening the neck are graphic depictions of how God desires internal devotion to reflect external obedience.
18 He enforces His justice for the powerless, such as orphans and widows, and He loves foreigners, making sure they have food and clothing. 19 You must love those foreigners living with you in the same way. Remember how you were foreigners in the land of Egypt! 20 So fear the Eternal your God; serve Him, and be devoted to Him. Show your loyalty by swearing oaths only in His name.