Psalms 32:1-6 (NKJV) BLESSED [is he whose] transgression [is] forgiven, [Whose] sin [is] covered.  Blessed [is] the man to whom the LORD does not impute iniquity, And in whose spirit [there is] no deceit.  When I kept silent, my bones grew old Through my groaning all the day long.  For day and night Your hand was heavy upon me; My vitality was turned into the drought of summer. Selah  I acknowledged my sin to You, And my iniquity I have not hidden. I said, "I will confess my transgressions to the LORD," And You forgave the iniquity of my sin. ?Selah  For this cause everyone who is godly shall pray to You In a time when You may be found; Surely in a flood of great waters They shall not come near him.
Psalms 32:1: This was quoted in Romans 4:6-8 and applied toward the New Covenant of grace. So, David was not speaking about something he had experienced but something he saw by faith that would be coming.
In a sense, God forgave Old Testament saints on credit. The blood of bulls and goats could never really take away sins (Hebrews 10:4). Only the perfect sacrifice of Jesus could do that (Hebrews 9:12). We have been made perfect and complete in our spirits (Hebrews 10:10, 14; and 12:23), which the O.T. saints never were.
So, David was prophesying about the better covenant that was to come (Hebrews 8:6). His sins were not forgiven as ours are. They were covered, but the sin nature remained (Romans 6:4, 6). Praise God for our New Covenant.
Psalms 32:2: When Paul quoted this verse in Romans 4:8 he said, "Blessed is the man to whom the Lord will not impute sin." Notice the emphasis on WILL NOT. The Lord doesn't only forgive us of past and present sins, but He has already dealt with our future sins (Hebrews 9:12, 15; 10:10, 14). Some people don't believe that is possible, but they better believe it is possible. Jesus only died for sins once, 2,000 years ago. If He can't forgive future sins, then no one today can be forgiven since all of our sins were future at that time.
Notice that David made special mention that this perfection is in the spirit. (See 2 Corinthians 5:17 and Hebrews 12:23.)
Psalms 32:3: The Amplified Bible translates this verse as "When I kept silence [before I confessed], my bones wasted away through my groaning all the day long." So, the Amplified Bible presents this as how David felt before he confessed his sin.
Psalms 32:4: David was describing how he felt before he confessed his sin (see my note at Psalms 32:3). This is describing the conviction of God on an unrepentant heart.
The phrase "my moisture is turned into the drought of summer" is followed by the word "Selah." Selah means "pause, and calmly think of that" (Amplified Bible). Resisting the conviction of God is like being in a desert. It's unbearable and will lead to death if we can't get out of it.
Psalms 32:5: David described how miserable he was before he confessed his sin. Here, he confessed his sin, and there was immediate forgiveness. This is a great lesson for us all (1 John 1:9).
What is the difference between "iniquity" and "sin"? The Hebrew word that was translated "iniquity" here is "'AWON." It was translated "iniquity" 220 times in the Old Testament. It means "perversity, i.e. (moral) evil" (Strong's Concordance). The first use of 'AWON in the Bible was in Genesis 4:13, where it was translated "punishment."
The Hebrew word "khat-taw-aw'" which was translated "sin" in this verse, means "an offence (sometimes habitual sinfulness), and its penalty, occasion, sacrifice, or expiation; also (concrete) an offender" (Strong's Hebrew Dictionary).
Exodus 34:7 uses the words "iniquity," "transgression," and "sin" in the same verse as is done here.
Psalms 32:6: David had described how miserable he was when he didn't yield to the conviction of the Lord (Psalms 32:3-4). Then he confessed his sin and received immediate forgiveness from the Lord (Psalms 32:5). Therefore, the godly should learn, like David did, to confess their sin and receive forgiveness.
Notice David said the godly will have to pray in a time when the Lord may be found. We cant take the Lord's willingness to forgive for granted. The Lord doesn't have to offer us unlimited opportunities for forgiveness. We can't come to the Lord unless He draws us (John 6:44). If the Lord quits dealing with our hearts, we are doomed.