Deuteronomy 30:6 - Matthew Poole's English Annotations on the Holy Bible

The Lord will circumcise thine heart, or, for the Lord will circumcise thine heart, i.e. will by his word and Spirit change and purge thy heart from all thine idolatry, and superstition, and wickedness, and incline thy heart to love him, as it here follows. See Deuteronomy 10:16. And so this is produced to show why and how those great things should be accomplished; God would first convert and sanctify them, the fruit whereof should be this, that they should return and obey God's commandments, Deuteronomy 30:8, and they should pros per in all things, Deuteronomy 30:9. The Hebrew vau is oft rendered for, and notes the reason of a thing, as 1 Kings 1:21, 1 Kings 18:3,4 Psa 1:3 5:12 Isaiah 16:2, Isaiah 64:5. And this promise principally respects the times of the gospel, and the grace which was to be then imparted to all God's Israel by Christ, by whom alone this circumcision is obtained, Colossians 2:11. And so having fully described to them the law of God, the rule of their obedience, here and in foregoing Chapter s, and considering their great instability in the performance of their obedience to it, he now seasonably adds a glorious gospel promise, and directs their faith to the Messias by whom alone they could expect or receive the establishment of their hearts in the ways of God against apostacy.