My wife is helping to lead a women's retreat this weekend, and she is stressing out about her talk: "Loving God with a Sincere Heart." As soon as I got home from my college fair, she confronted me: "Help!" she said, "I don't know what to write!" It got me thinking about what a sincere heart really is, and who possesses it.
My models for sincerity are David (in the Old Testament) and Peter (in the New Testament). I don't know why, but I always equate the two together, like Peter is the New David in some way. David danced in a loin cloth before the Lord, he didn't care what people thought. He ate the showbread because he was hungry. He sinned boldly, but was quick to see his own fault, and humble enough to admit it. And he loved the Lord madly. Psalm 51, which was written after Nathan the prophet confronts David after his affair with Bathsheba, says of the Lord, "you insist on sincerity of heart."
Peter was brazen, but only because he loved the Lord with everything he had. When Peter said, "though all may fall away, I will not fall away," he was being sincere. But he was wrong, too! He did fall away, but his sincerity displayed itself in the tears of shame he wept after realizing he had denied Jesus, and was being shown what he was at that time: a hypocrite, a liar, a bad friend.
But was this all Peter was? Does his denying Christ reduce him to just that--a denier? Jesus did not reduce Peter to what he was at that moment; rather, he saw him in his entirety. Part of sincerity is not pretending to be anything other than what you are--a sinner--while at the same time not reducing yourself to that identity. It is having "eyes to see."
In chapter 18 of the book of John, Peter is denying Christ three times. By chapter 21, Jesus is asking Peter, "do you love me?" and Peter has the audacity to proclaim three times, "Lord, you know that I do." Is he being sincere? I believe he is. So moral failing and sincerity must have something to do with one another. Someone could say, "he is not sincere because what he says (I love you) does not match up with his actions (I don't know you). Peter does not get "stuck" on his imperfection, but boldly proclaims his love for Christ in spite of it.
Sincerity (like repentance) comes from the heart...not the mind. The heart is not perfect, but it can be, I believe, perfectly sincere. And a sincere heart does not pay heed to those who stand in judgment of it, dredging up the sins of the past and wagging them in front of it, because it knows that only God can judge the heart, for "man sees the appearance but the Lord looks into the heart" (1 Samuel 16:7).