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.