Bible Notes Online - Malachi 4 - ESV
Commentary

v1: Judgment inevitable for the wicked, and the proud. They will be burned up, without hope, having no more opportunity to repent.

v2-3: Victory for the faithful, since God makes a distinction between the righteous and the wicked. The Lord Jesus is the Sun of Righteousness; from Malachi's perspective, He is yet to arise.

v4: Remember! For even the people of God tend to forget the truths of God.

v5-6: Elijah, picturing John Baptist; the forerunner, or predecessor, coming with a warning, as well as preparing the way for the Lord.