Deuteronomy 30:6

And the Lord thy God will circumcise thine heart, and the
heart of thy seed
No mention is made of circumcision of the flesh, which will now be out of use with the Jews; they being fully convinced of the abrogation of the ceremonial law by the Messiah, whom they will now receive. It is spiritual circumcision only that is here spoken of, with which the Jews will be circumcised, when they shall be pricked and cut to the heart, and be thoroughly convinced of sin; when the iniquity of their hearts will be laid open to them, and they put to pain, and filled with shame and loathing for it; when the hardness of their hearts will be removed, and the foolishness of them will be exposed and taken away, and they will be made willing to part with their sins, and with their own righteousness; when the graces of the Spirit will be implanted in them, and the blood of Christ applied to them for pardon and cleansing. This is the circumcision made without hands, which is not of men, but of God; what he calls for, and exhorts unto, as being necessary, ( Deuteronomy 10:16 ) ; he here promises to do; and deed none but himself can do it; for he only can come at the hearts of men, to take anything out of them, or put anything into them; it is he that opens the heart, softens, quickens, enlightens, and purifies it: Baal Hatturim says this respects the times of the Messiah:

to love the Lord thy God with all thine heart, and with all thy soul;
which, though the duty of every man, is performed by none but those that have the grace of God; there is no love to God in the heart before this inward and spiritual circumcision of it: it is a fruit of the Spirit in conversion when the affections are taken off of other things, and set on Christ; when a man sees his sin and his Saviour, and the one is odious, and the other precious; when the blessings of grace are applied, and the love of God is shed abroad in the heart, which cause love to God and Christ again:

that thou mayest live;
spiritually and eternally; for there is no spiritual life in the soul till the heart is circumcised, or, in other words, regenerated and renewed; then it is quickened; then a man lives a life of faith on Christ, of holiness from him, communion with him, and has both an open right unto, and meetness for, eternal life.