Deuteronomy 13:18
When thou shalt hearken to the voice of the LORD thy God, to keep all his commandments which I command thee this day, to do that which is right in the eyes of the LORD thy God. When thou shalt hearken to the voice of the LORD thy God, to keep all his commandments which I command thee this day, to do that which is right in the eyes of the LORD thy God.
Deuteronomy 13:18 stands within the section of Deuteronomy that reviews the law for Israel's new generation before crossing the Jordan River into the promised land. Deuteronomy means repetition of the law, a rehearsal of the wonderful things God had done for His people and of the chief laws connected with Israel. After caring like a loving father for the often rebellious people through forty years of wandering in the wilderness, Moses could not go with them into the promised land because he had yielded in impatience to hasty words glorifying himself instead of God. Before leaving them he solemnly brought to their remembrance the lessons God had taught them during the forty years and impressed upon them the sacred import of God's holy law and the necessity of keeping it.
The expression this day is part of a solemn, emphatic statement, reflecting an Old Testament idiom that often accompanies a verb of assertion. The verse requires heeding the voice of the Lord God, keeping all His commandments, and doing what is right in His sight. Its surrounding teaching provides a good test by which to try prophets, making God's law the standard so that anyone who leads people away from that law is false even if signs and wonders accompany the message.
The chapter shows the curse that follows breaking the first two precepts of God's law, with wilful transgression of the commandments bringing the transgressor under the curse. The verse is counted among laws of the Hebrew civil code that carried penalties enforced by the magistrate, and those penalties foreshadow the final punishment of the ungodly. The directions in the chapter were what Jewish leaders hoped to use to convict the apostles of sorcery and put them to death.