Matthew Poole and continuators on Deuteronomy 30:10

10 If thou shalt hearken unto the voice of the LORD thy God to keep his commandments and his statutes which are written in this book of the law, and if thou turn unto the LORD thy God with all thine heart, and with all thy soul.

This caution and condition is added to warn them that they should not receive the Grace of God in vain, and to teach them, that the Grace of God doth not discharge mans obligation to his duty, nor excuse him for the neglect of it, and that Conversion and Sanctification, though it be Gods work, yet it is mans duty.