Proverbs 13:9 - Ellicott's Commentary On The Whole Bible

The light of the righteous rejoiceth — i.e., burns joyously, as the sun “rejoiceth as a giant to run his course” (Psalms 19:5). A distinction may be drawn between the “light” of the righteous and “lamp” of the wicked. The one walks in the “light” of God’s truth, and so his path becomes continually more plain (see above on Proverbs 6:23); the other walks by the glimmer of his own “lamp,” the “fire” and “sparks” of his own kindling (Isaiah 50:11), the fancies of his own devising, and so his end is darkness. But this distinction is not always observed (comp. Job 18:5-6, where “light” and “lamp” are both applied to the wicked.)