Adam Clarke on Proverbs 13:9

The light of the righteous rejoiceth - They shall have that measure of prosperity which shall be best for them; but the wicked, howsoever prosperous for a time, shall be brought into desolation. Light and lamp in both cases may signify posterity. The righteous shall have a joyous posterity; but that of the wicked shall be cut off. So 1Kgs 11:36 : "And unto his son will I give one tribe, that David my servant may have a light (נר ner, a lamp) always before me." 1Kgs 15:4 : "Nevertheless for David's sake did the Lord give them a lamp, to set up his son after him." See also Psa 132:17, and several other places.