Who can understand his errors? Cleanse me from secret faults. Keep back Your servant also from presumptuous sins; let them not have dominion over me. Then I shall be blameless, and I shall be innocent of great transgression.
Listen to the "Verse by Verse" episode covering this scripture.
As we covered previously (Psalm 19:7-9; 10-11), in this psalm David has been praising God for the good and beneficial law He has given to us. Without the law, we would not understand the cause of blessings (obeying God’s law) and the cause of suffering and death (sin—disobedience to God’s laws; Deuteronomy 28:1-2, 15).
(Of course, sometimes the blessings for obedience and the curses for disobedience are delayed in this world under the sway of the wicked one. Read more about this in our articles “When Life Doesn’t Make Sense,” “Is Life Fair?” and “Why Am I Suffering?”)
God’s law shows what sin is (Romans 7:7; 1 John 3:4). Looking into the law helps us to see ourselves and what we need to change (James 1:23-25).
Still, David realized that we have blind spots. We may not recognize some sins in our own lives, but they are not secret to God. Asking God to cleanse us of secret sins implies more than just asking Him to forgive them. We need God to reveal them to us so we can commit to change and seek His help to overcome these sins.
David also prayed about avoiding presumptuous sins, which are called great transgressions because no sacrifice was accepted for them (Numbers 15:28-31). We all sin unintentionally, but woe to those who sin presumptuously—“‘with a high hand,’ with open disdain for the will and work of God” (NKJV Study Bible, note on Numbers 15:30-31).