Here is a reference to the first and to the second coming of Christ: God has fixed the day of both. Those who do wickedly, who do not fear God's anger, shall feel it. It is certainly to be applied to the day of judgment, when Christ shall be revealed in flaming fire; to execute judgment on the proud, and all that do wickedly.
In both, Christ is a rejoicing Light to those who serve him faithfully. By the Sun of Righteousness we understand Jesus Christ. Through him believers are justified and sanctified, and so are brought to see light.
His influences render the sinner holy, joyful, and fruitful. It is applicable to the graces and comforts of the Holy Spirit, brought into the souls of men. Christ gave the Spirit to those who are his, to shine in their hearts, and to be a Comforter to them, a Sun and a Shield.
That day which to the wicked will burn as an oven, will to the righteous be bright as the morning; it is what they wait for, more than those that wait for the morning. Christ came as the Sun, to bring, not only light to a dark world, but health to a distempered world.
Souls shall increase in knowledge and spiritual strength. Their growth is as that of calves of the stall, not as the flower of the field, which is slender and weak, and soon withers. The saints' triumphs are all owing to God's victories; it is not they that do this, but God who does it for them.
Behold another day is coming, far more dreadful to all that work wickedness than any which is gone before. How great then the happiness of the believer, when he goes from the darkness and misery of this world, to rejoice in the Lord for evermore!