John Gill Commentary Deuteronomy 26:16

"This day Jehovah thy God commandeth thee to do these statutes and ordinances: thou shalt therefore keep and do them with all thy heart, and with all thy soul." — Deuteronomy 26:16 (ASV)

This day the Lord your God has commanded you 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:

you shall therefore keep and do them with all your heart, and with all
your soul ;
cordially, readily, willingly, sincerely, constantly, and to the utmost of their abilities.