Deuteronomy 27:9
And Moses and the priests the Levites spake unto all Israel, saying, Take heed, and hearken, O Israel; this day thou art become the people of the LORD thy God. And Moses and the priests the Levites spake unto all Israel, saying, Take heed, and hearken, O Israel; this day thou art become the people of the LORD thy God.
The speakers are Moses together with the priests the Levites, addressing all Israel with a call to take heed and hearken with careful attention, on the ground that on that day Israel became the people of the Lord God. That declaration stands connected with keeping all the commandments that day, and with writing all the words of the law very plainly on great plastered stones to be set up on Mount Ebal after passing over Jordan into the land flowing with milk and honey. There an altar of whole stones untouched by any iron tool was to be built, with burnt offerings and peace offerings offered, and with eating and rejoicing before the Lord, preparing for the charge to obey the voice of the Lord and do His commandments and His statutes.
The verse belongs to the directions in Deuteronomy 26 through 28 that plainly state the blessings of obedience, and it is to be read carefully together with all of Deuteronomy 26 and with Deuteronomy 28. It expresses the principles of the law of God's kingdom, made clear and specific so that obligations are plain and minds are not left in ignorance and uncertainty. The words were spoken by Jesus Christ Himself, enshrouded in the pillar of cloud, with His own voice.
Obedience to God's commandments is for present and future good and brings prosperity, while disobedience brings a curse. The duties it teaches remain binding because God's gifts continue. It places a never-ceasing obligation on all whom God has blessed with life and health and temporal and spiritual advantages to publicly acknowledge His special favor, so that God's name will be glorified as a testimony that His Word is true and trustworthy.