(Summarizing an editorial by D. A. Carson in Themelios)
When it comes to a Christian’s progress in holiness, Scripture comes at the matter in at least two different ways. On one side of the equation are passages that teach only two ways (like Ps 1): one way, the way of the sinner, leads to death. The other way, the way of the holy, leads to life. There is no middle ground. We are to be holy, or we will not see the Lord (Heb 12:14). Only the pure in heart will see God (Mt 5:8). The child of God doesn’t sin; sinners are children of the devil (1 Jn 3:6-10).
But there is another set of passages which faithfully present God’s people as righteous and sinful. They have shining moments of faith and dark moments of unbelief. Thus does Abraham leave Ur by faith, but sometime later does he travel to Egypt in fear. Thus does David love God passionately on the one hand, and thus does he lustily embrace Bathsheba on the other.
Both kinds of Scripture are helpful. The absolute passages keep us striving for holiness, while narratives of flawed saints keeps us humble and hopeful; humble because we recognize the same tendencies within us, and hopeful because we see that God loves his flawed people.