This statement came from Psalm 51:10, where David was writing in the aftermath of his sin with Bathsheba. He had stated, “Purge me with hyssop, and I shall be clean; Wash me, and I shall be whiter than snow. Make me hear joy and gladness, That the bones You have broken may rejoice. Hide Your face from my sins, And blot out all my iniquities” (vv. 7-9). David knew the horribleness of his sin and his need of forgiveness. His heart was broken by sin.
However, forgiveness was not David’s only need. Going forward, he needed the ability to shun temptation. His plea in v. 10 begs for a clean heart. A clean heart can keep one from being led into temptation (Philippians 4:8; cp. Matthew 6:13). Focusing on purity keeps the heart clean.
A third part of David’s petition in Psalm 51 is contained in v. 13: “Then I will teach transgressors Your ways, And sinners shall be converted to You.” A natural progression of someone who has committed sin is to be convicted of it, desire a pure heart, and then tell others about sin. David was willing to teach the lost about God so they could be converted. Everyone who has been redeemed by the blood of Christ should take this to heart. Talk to someone who is lost. Teach them the gospel. Help them find the way to the salvation of their sins.