Answer:

The lamp of the wicked, also referred to as “the light of the wicked” (Job 18:5, ESV), signifies the prosperity that is enjoyed by many evil people in this world. The lamp of the wicked is that which causes them to “shine” in the world; it is a poetic description of their happiness, wealth, honor, and respected status. Their spiritual condition is dark, but they enjoy a spark of glory despite their evil hearts. The lamp of the wicked is also mentioned in Job 21:17, Proverbs 13:9, and Proverbs 24:20.

Sadly, the light of the lamp of the wicked man’s wealth and success will eventually go out, revealing the utter hopelessness of his condition. Proverbs 13:9 contrasts the lamp of the wicked to the light and life of the righteous:
“The light of the righteous shines brightly,
but the lamp of the wicked is snuffed out.”

The contrast between the righteous and the wicked could not be plainer: the glory and success of the righteous will last, as opposed to the fleeting splendor of the wicked. An evil man may enjoy his “fifteen minutes of fame,” but the godly will celebrate a triumph that lasts into perpetuity. The Amplified Bible brings out the contrast more strongly:
“The light of the righteous [within him—grows brighter and] rejoices,
But the lamp of the wicked [is a temporary light and] goes out.”

We have a treasure in earthen vessels, “for God, who said, ‘Let light shine out of darkness,’ made his light shine in our hearts to give us the light of the knowledge of God's glory displayed in the face of Christ” (2 Corinthians 4:6). Those who have the light of the gospel shining in their hearts and the illumination of spiritual knowledge have a light of joy that will never be extinguished. Their light will shine eternally, a light like that of the sun, bright with warmth. But the light of the wicked is dim and dull by comparison. Their prosperity is short-lived, their joys momentary, and the pleasures derived from sin but for a season. The ultimate end of the righteous is to live eternally in the New Jerusalem, which “does not need the sun or the moon to shine on it, for the glory of God gives it light, and the Lamb is its lamp” (Revelation 21:23). The lamp of wicked, however, will be extinguished, leaving them forever in “outer darkness” (Matthew 8:12).

Job, in his argument with his “comforters,” notes that often evil men live and prosper just as long as righteous men, and their evil deeds are not always recompensed in this life: “How often is the lamp of the wicked snuffed out? How often does calamity come upon them, the fate God allots in his anger?” (Job 21:17). Job is saying that God withholds His wrath upon the wicked, and many may prosper in this life. The answer to Job’s question “how often is the lamp of the wicked snuffed out?” is “not always.” Many continue to prosper in this life, but Scripture promises that justice will prevail (see Psalm 73).

Therefore, Proverbs 24:19–20 tells us, we are not to despair when we see evildoers prosper in this life:
“Do not fret because of evildoers
or be envious of the wicked,
for the evildoer has no future hope,
and the lamp of the wicked will be snuffed out.”

The wicked have no hope of everlasting happiness, a condition for which they should be pitied, not resented. They have their good things now, but their just rewards lie ahead (see Luke 16:25). They are not to be envied. The lamp of the wicked is of short duration. The godly are in a much more blessed condition:
“You, LORD, keep my lamp burning;
my God turns my darkness into light” (Psalm 18:28).