This day the Lord thy God. He again reminds them that God is the author of the Law, in order that His majesty should the more impress them; and not only so, but that, since the Law was specially delivered to them, its observation was the more enjoined upon them. Hence he exhorts them earnestly to apply their hearts to those things which God had enjoined them to keep, because men grow careless in their duties, unless they are often stirred up. For, undoubtedly, God indirectly rebukes the people's indifference, by so often calling them to obedience. By the words "with all thy soul" is meant serious apprehension, and carefulness, as well as sincerity, free from all disguise and deceit. For nothing is more displeasing to God than hypocrisy, because He seeth the heart. If any object that it was vain to demand of them what no mortal can perform, viz., to keep the Law with all their heart, I reply, that all the heart is opposed to a double or divided heart, and is equivalent to entire, or altogether without deceit, although (as we shall hereafter see) it is not absurd to propose to believers an object, at which they are to aim, although they may not attain to it as long as the weakness of the flesh hinders them.

A brief and earnest exhortation by way of conclusion to the second and longest discourse of the book.

This day the LORD thy God hath commanded thee to do these statutes and judgments: thou shalt therefore keep and do them with (n) all thine heart, and with all thy soul.
(n) With a good and simple conscience.

This day the Lord thy God hath commanded thee to do these statutes and judgments,.... These are the words of Moses, as Aben Ezra rightly observes, and refer not only to the laws last mentioned, but to all others which he had repeated, or the Lord by him had ordered to be observed, recorded in this book: and though it is very probable Moses had been several days repeating former laws, and acquainting them with new ones; yet this being the last day, in which the whole account was finished, they are said to be commanded that day, and though commanded that day were to be observed and done every day; for, as Jarchi says, every day was to be considered and reckoned as new, as if on that day they were commanded them:
thou shall therefore keep and do them with all thy heart, and with all thy soul; cordially, readily, willingly, sincerely, constantly, and to the utmost of their abilities.

Moses here enforces the precepts. They are God's laws, therefore thou shalt do them, to that end were they given thee; do them, and dispute them not; do them, and draw not back; do them, not carelessly and hypocritically, but with thy heart and soul, thy whole heart and thy whole soul. We forswear ourselves, and break the most sacred engagement, if, when we have taken the Lord to be our God, we do not make conscience of obeying his commands. We are elected to obedience, 1-Peter 1:2; chosen that we should be holy, Ephesians 1:4; purified a peculiar people, that we might not only do good works, but be zealous in them, Titus 2:14. Holiness is true honour, and the only way to everlasting honour.

At the close of his discourse, Moses sums up the whole in the earnest admonition that Israel would give the Lord its God occasion to fulfil the promised glorification of His people, by keeping His commandments with all their heart and soul.