Malachi4chapter 4

Remember ye the law of Moses my servant: Before naming Elijah the book turns back to Moses, the two figures the Gospels will later set beside Christ at the transfiguration. Remembering the law given at Horeb, with its statutes and judgments, is the last positive command the Old Testament gives Israel, closing four hundred years of prophetic silence by pointing back to Sinai rather than forward to something new. Wesley and Henry read the verse as a summary charge, that whatever else the disputers of this book had questioned, the law itself remained settled and binding until the messenger named at 3:1 and again in verse 5 should come.

I will send you Elijah the prophet: The last prophet of the Old Testament names the next one by name, Elijah, before the great and dreadful day of the Lord arrives. The Lord Jesus identifies John the Baptist as the fulfillment at Matthew 11:14 and Matthew 17:11-13, and Luke 1:17 has the angel tell Zacharias that his son will go before the Lord in the spirit and power of Elias, a reading the exposition states as the New Testament's own. Alongside it stands the older Jewish expectation, kept alive in the synagogue's practice of setting a cup and an empty chair for Elijah at Passover, and a further Christian reading that looks for a future forerunner ministry yet to come, both held by the bench without a verdict pressed on the reader.

turn the heart of the fathers to the children: The last sentence of the Hebrew canon's arrangement turns on relationship and its opposite, Elijah's ministry to turn the heart of fathers to children and children to fathers, or the Lord comes and smites the earth with a curse. The Old Testament as English Bibles order it ends on that word, curse, four hundred years of silence before the New Testament opens with a genealogy, the record of the very fathers and children this verse names, tracing Jesus Christ's descent from Abraham and David. The synagogue reading tradition takes note of the ending too, repeating verse 5 aloud after verse 6 so that the public reading never stops on the word curse, a practice the commentators record as evidence of how heavily the verse has always been felt. Keil reads the turning of hearts as revival preparing a people to receive their Messiah rather than a bare family reconciliation, the last word before four centuries of silence and then the announcement of Gabriel to Zacharias.