In different places, the Lord presents the day of his coming as a day when the righteousness of those who feared God will be publicly revealed and rewarded. In Psalm 37:6 the psalmist wrote that those who commit their ways to the Lord and who trust him will be rewarded in the day that he acts. And this is the reward: He will bring forth [their] righteousness as the light, and [their] justice as the noonday.
That is, just as the sun rises to dispel the darkness, so the Lord will come to his people, and bring light to those who sit in darkness, that is, bring deliverance to those who suffer the miserable consequences of sin. This same image is conveyed in Isaiah 58:8, where God promises his people that if they would truly repent of their sin, then God would turn to them in favour, and then shall [their] light break forth like the dawn, and [their] healing shall spring up speedily; [their] righteousness shall go before [them].
2 But for you who fear my name, the sun of righteousness shall rise with healing in its wings. You shall go out leaping like calves from the stall.