They have many scars and spots

(Thomas Watson, "The Godly Man's
Picture Drawn with a Scripture Pencil)

"He has not beheld iniquity in Jacob." Numbers 23:21

"Let us draw near to God with a sincere heart." Heb. 10:22

If the heart is sincere, God will wink at many failings. 
God's love does not make Him blind; He can see our
infirmities. But how does God look at a believer's sins?
Not with an eye of revenge—but of pity, as a physician
sees a disease in his patient—so as to heal him. God
does not see iniquity in Jacob—so as to destroy him;
but to heal him!

How much pride, vanity, passion, does the Lord pass
by in His sincere ones! He sees the integrity—and
pardons the infirmity. We esteem a picture, though
it is not drawn full length. Just so, the graces of God's
people are not drawn to their full length. They have
many scars and spots
—yet being sincere, they shall
find mercy. God loves the sincere, and it is the nature
of love to cover infirmity.