God closes the last book of the Old Testament with conditional promises of blessing and curse:
Remember the Law of Moses, My servant, which I commanded him in Horeb for all Israel, with the statutes and judgments. Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the Lord. And he will turn the hearts of the fathers to the children, and the hearts of the children to their fathers, lest I come and strike the earth with a curse" (Mal. 4:4-6).
If there is not repentance for this covenant-breaking, God promises swift and severe and judgment―curses on the individuals and upon the land, leaving them "neither root nor branch." "…lest I come and smite the land with a curse." Notice also that the specific requirement was to "Remember the law of Moses My servant, even the statutes and ordinances which I commanded him in Horeb for all Israel." As Abraham was to command his children and household to "command his children and his household after him, that they keep the way of the Lord, to do righteousness and justice." So, we must understand that the law is the perfect expression of that very justice and righteousness he was to teach. Joshua 1:8: "This book of the law shall not depart out of thy mouth…" Love for God is expressed by keeping His law, as Jesus said, "If you love Me, keep My commandments" (John 14:15). It is not some vague or sentimental standard that God requires when it comes to covenant household. It is His word, and His word alone that is to provide the our instruction:
But you must continue in the things which you have learned and been assured of, knowing from whom you have learned them, and that from childhood [infancy] you have known the holy Scriptures, which are able to make you wise for salvation through faith which is in Christ Jesus. All Scripture is given by inspiration of God and is profitable for doctrine, reproof, correction and instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work (2 Tim. 3:14-17).
In the opening of the New Testament (Luke 1:17) an angel tells Zacharias that his son, John the Baptist, would be that prophet, Elijah, who would "turn the hearts of the fathers to the children." It is clear that household fidelity is at the heart of the work of the gospel. When men and women are converted to Christ, the primary place where the power of the redemptive work should be seen is in the restoration (i.e., redemption), of the covenant household. The family relationships are set in order according to the pattern of God's word. Not only do fathers (and mothers as their husband's covenant companion), focus their affection and attention toward the godly raising of their children, but also the children come to have their hearts affectionately directed toward their godly parents.