As if the number of our sins we do recognize isn’t large enough, it’s astounding to consider that there are many more we don’t even realize we commit. Such is the result of living with a sinful heart. Jeremiah understood. “The heart is deceitful above all things and beyond cure. Who can understand it?” (Jeremiah 17:9).

There are probably two chief areas in which these “sins of ignorance” are hidden from our eyes. The first are sins hidden from us because we don’t know Scripture well enough. After reading some passage of Scripture, who of us hasn’t suddenly become aware of a sin of heart and life with a clarity previously hidden?

Sins may also be hidden from us because we are unaware of the impact our words and actions have on others around us. At times our words and actions, perhaps innocent enough to us, may have hurt another or caused them to stumble in their faith. All the while we may be clueless about how what we said or did hurt them.

When it comes to being ignorant of our sins, such ignorance is not bliss. Sin, whether known or unknown, is never strengthening to faith—ours or others’. Sin is always at work—whether we realize it or not—to destroy faith.

Certainly persisting in sins of which we are aware brings the most immediate danger of falling from faith. Yet even sins of which we are unaware can have a cancerous effect on faith.

That’s why we join David in this humbling confession: “Who can discern his errors? Forgive my hidden faults” (Psalm 19:12). That is the same encouragement Martin Luther gives as he writes about confession in the Small Catechism. “Before God we should plead guilty of all sins, even those we are not aware of, as we do in the Lord’s Prayer.” As we run to Christ’s cross with that burden of guilt, it’s comforting to know that “the blood of Jesus, his Son, purifies us from all sin” (1 John 1:7). That “all sin” from which Christ purifies us includes not only sins of which we are aware, but also those hidden from our eyes.