Proverbs 26:24-26 describes harboring deceit in the heart — the exact scenario from 12:20, with exposure promised.

Matthew 5:9 blesses peacemakers as sons of God, fulfilling the promise of joy for those who plan peace in the proverb.

Mark 7:21 traces evil deeds to the heart, aligning with 12:20's claim that deceit originates in the heart of evil planners.

Psalm 140:2 describes those who 'plan evil in their heart' and stir up war—the opposite of the peace planners in the proverb, highlighting the contrast.

In Daniel 11:27, two kings with hearts bent on evil and speaking lies mirror the deceitful hearts of those who devise evil in this verse.

In Mark 7:22, deceit is listed among evils from the heart, echoing the proverb's 'deceit in the heart' and showing its broader moral context.

Romans 12:18 urges living peaceably with all, echoing the promise that those who plan peace have joy in this verse.

Hebrews 12:14 exhorts striving for peace with everyone, expanding the proverb's call to plan peace into active pursuit.

Romans 1:29 lists deceit among sins of those who suppress truth, reinforcing the link between deceit and evil from the heart.