In Psalm 51, David famously wrote-
Create in me a clean heart, O God,
And renew a steadfast spirit within me.
Do not cast me away from Your presence
And do not take Your Holy Spirit from me.
Restore to me the joy of Your salvation
And sustain me with a willing spirit.
Then I will teach transgressors Your ways,
And sinners will be converted to You.
(Psalm 51:10-13)
His is a magnificent statement of repentance. No wonder God called David a man after His own heart. (Acts 13:22).
You notice that David 's contrition and petition for restoration didn't include restoring a kingdom to him, or his fortress or his armor or his lands. He did not ask for material things. He wanted the 'joy of God's salvation' - spiritual things. David wanted the spiritual joy of a right relationship with His God.
I often ponder the joy of my salvation. I don't want to lose that wonder and awe of the miracle of a purified mind and a clean heart. Maybe it's because I came to the Lord in my 40s, and I remember so well the feeling of moral confusion, impurity, and guilt. One thing I enjoy about salvation is the release of my mind from having to work so hard to justify my sin. Or the efforts of my heart to hide it. Or the difficulty in having my conscience making valiant efforts to tamp down the morally questionable things I said and did.
A willing spirit that finds joy in knowing and obeying our Savior is a release that can only come from Jesus. It's a gift to us, borne on His blood and His cross. In gratitude, David said he would teach others the ways of God so that sinners would be converted. He is passing along the gift he himself thirsts for and treasures.