Proverbs 24:8
He that deviseth to do evil shall be called a mischievous person.

Proverbs 6:14
Frowardness is in his heart, he deviseth mischief continually; he soweth discord.

1 Samuel 23:9
And David knew that Saul secretly practised mischief against him; and he said to Abiathar the priest, Bring hither the ephod.

and their lips declare trouble
This part of the verse focuses on the outward expression of the wicked's inner thoughts. The lips, representing speech, are used to spread trouble, which can mean deceit, slander, or incitement to conflict. This reflects the biblical principle that words have power (Proverbs 18:21). The connection between heart and speech is a recurring theme in Scripture, as seen in Luke 6:45, where Jesus teaches that the mouth speaks what the heart is full of. The cultural context of the time placed significant importance on spoken words, which could influence public opinion and incite actions. This serves as a caution against the influence of those who use their words to cause harm, aligning with the broader biblical call to guard one's speech (James 3:5-6).

“for their hearts devise violence” pulls back the curtain on what drives the wicked. The issue is not merely bad behavior; it is a heart that plots harm.

• Scripture consistently locates sin’s birthplace in the heart. Genesis 6:5 says, “every inclination of the thoughts of his heart was altogether evil all the time,” and Matthew 15:19 echoes, “For out of the heart come evil thoughts….”

• Violence is intentional, not accidental. Proverbs 6:18 lists “a heart that devises wicked schemes” alongside “feet that run swiftly to evil.” The same deliberate planning is in view here.

• The warning in Proverbs 4:23, “Guard your heart with all diligence, for from it flow springs of life,” stands in stark contrast. A guarded heart is the antidote to a heart scheming violence.

• Romans 3:15–16 observes of the ungodly, “Their feet are swift to shed blood; ruin and misery lie in their wake.” The bent toward violence begins long before any outward act.

• Practically, the verse reminds us that friendship or admiration of such people (24:1) is dangerous because their plans are shaped by an inner appetite for harm.

The second half exposes the overflow: “and their lips declare trouble”. What is brewing inside inevitably spills out.

• Psalm 10:7 describes the wicked: “His mouth is full of cursing, deceit, and violence.” The pattern matches our proverb—violent intent expressed in speech.

• Proverbs 15:28 contrasts this with the righteous: “The heart of the righteous weighs its answers, but the mouth of the wicked gushes evil.” Words reveal character.

• James 3:6 calls the tongue “a world of iniquity,” capable of setting “the whole course of one’s life on fire.” When lips “declare trouble,” they ignite conflict around them.

• “Trouble” includes threats, slander, false accusations, and stirring up strife (Proverbs 16:28; 26:20-21). Such speech wounds relationships and communities.

• Luke 6:45 sums it up: “Out of the overflow of the heart the mouth speaks.” A heart plotting violence will naturally voice it—whether through bragging, intimidation, or manipulation.

Proverbs 24:2 exposes the progression of evil: an unguarded heart cultivates violent schemes, and lips become the loudspeaker for those schemes. Recognizing this chain protects us from envying or joining the wicked (24:1) and urges us instead to keep hearts renewed by God’s Word and mouths committed to speaking peace and truth.