The Geneva Bible Translation Notes, [1599], at sacred-texts.com
(a) He prophesies of God's judgments against the wicked, who would not receive Christ, when God would send him for the restoration of his Church.
But unto you that fear my name shall the (b) Sun of righteousness arise with healing in his wings; and ye shall go (c) forth, and grow up as calves of the stall.
(b) Meaning, Christ, who with his wings or beams of his grace would enlighten and comfort his Church; (Eph 5:14). And he is called the "Sun of righteousness", because in himself he has all perfection, and also the justice of the Father dwells in him: by which he regenerates us to righteousness, cleanses us from the filth of this world, and reforms us to the image of God.
(c) You will be set at liberty, and increase in the joy of the Spirit; (Co2 3:17).
(d) Remember ye the law of Moses my servant, which I commanded unto him in Horeb for all Israel, [with] the statutes and judgments.
(d) Because the time had come that the Jews would be destitute of Prophets until the time of Christ, because they should with more fervent minds desire his coming, the Prophet exhorts them to exercise themselves diligently in studying the Law of Moses in the meantime, by which they might continue in the true religion, and also be armed against all temptations.
Behold, I will send you (e) Elijah the prophet before the coming of the great and (f) dreadful day of the LORD:
(e) This Christ interprets of John the Baptist, who both for his zeal, and restoring or religion, is aptly compared to Elijah; (Mat 11:13-14).
(f) Which as it is true for the wicked, so does it waken the godly, and call them to repentance.
And he shall (g) turn the heart of the fathers to the children, and the heart of the children to their fathers, lest I come and (h) smite the earth with a curse.
(g) He shows in what John's office would consist: in the turning of men to God, and uniting the father and children in one voice of faith: so that the father will turn to the religion of his son who is converted to Christ, and the son will embrace the faith of the true fathers, Abraham, Isaac, and Jacob.
(h) The second point of his office was to give notice of God's judgment against those that would not receive Christ.