Through sin left in us, we are made more and more to feel our need for Christ, and his precious blood for the removal of our guilt daily contracted anew, and for the strengthening of our souls in our Christian course, so that we come out of the wilderness resting upon our Beloved.  So we see that our security is not in our hand; if it were, we would be quickly lost.

“Why do I keep struggling with the same sinful thoughts?”  “Why can’t I just gain victory over lust and pride?”  “Why in the world does God allow sin to remain in his people?”  These are questions Christians ask from time to time.  We think of how nice it would be if we didn’t have to struggle with sinful thoughts, words, and deeds.  But, in his sovereignty, God has a reason for allowing sin to remain in his children.  Thomas Boston (d. 1732) gave some helpful answers to the question of why God allows sin to dwell in his elect while on earth.  Here are some of Boston’s answers (which I’ve edited and summarized):

1. God has ordered the matter of the believer’s sanctification, that sin is left to be active in their souls while here on earth, for their further humiliation.  For example, God gave Paul a thorn in the flesh to keep him low.  And so we find David, after his grievous fall, grows in the grace of humility.
2. The Lord allows sin to remain in his people so they are stirred to the frequent exercise of prayer.  The soul feels the continual need of pardon, and therefore must be much lying at God’s footstool.  When his children grow remiss in their duty, the Lord sometimes allows them to fall into some grievous sin to awaken them and wound their conscience, so they cry to Him like a child who falls into a small fire.
3. The sin left in us makes us more watchful of our hearts which still are prone to wander.  When a prisoner escapes, and they catch him, they will put him in more close custody than before.  We walk through a world filled with many snares; if we were not watchful, we would be caught in them.
4. Just like God allowed some Canaanites to remain in the land to try his people, so he has left remains of natural corruption in them for their exercise and trial.  Therefore Christ’s soldiers know whom they fight against, and by whose strength they may overcome.  God gives his people armor at their conversion; is it reasonable that it should lie beside them rusting?  Indwelling sin makes us lean on Christ’s strength and use God’s armor in the battle.
5. Through sin left in us, we are made more and more to feel our need for Christ, and his precious blood for the removal of our guilt daily contracted anew, and for the strengthening of our souls in our Christian course, so that we come out of the wilderness resting upon our Beloved.  So we see that our security is not in our hand; if it were, we would be quickly lost.
6. It is God’s ordinary way to bring about a great work by degrees – including the great work of the believer’s sanctification.  God could have created all things in one moment; instead, he was pleased to take six days to do it.  He could have sent Christ immediately after Adam fell, but he instead let thousands of years pass.  He could have brought Israel to the Promised Land immediately; instead it pleased him that they should wander in the wilderness for forty years.  So it is with sanctification.
7. Finally, through the indwelling sin that remains, Christ is glorified.  While the enemy (sin) does dwell in us, Christ’s grace and Holy Spirit are at work in us so that the enemy cannot overcome, domineer, or destroy us.  Because of indwelling sin we know that we cannot justify ourselves, but can only be justified by the perfect obedience of Christ, which we lay hold of by faith.  In this, Christ is glorified.

After noting these seven points, Boston wrote, “To see how God makes such an excellent medicine of such poisonous ingredients cannot be but very delightful.”  The struggle against indwelling sin is difficult for sure.  But when we remember God’s sovereign use of indwelling sin in his people for their good and his glory, it helps us press on in the faith with our eyes fixed on Jesus.  He will one day graciously give us the full victory over sin.

Near the end of the treatise, Boston wrote this:

“Finally, to shut up [summarize/end] all; it is plain, that the more difficulties the work of man’s salvation is carried through, the free grace of God is the more exalted; our Lord Jesus, the author of eternal salvation, hath the greater glory: but in this way it is carried on over the belly of more difficulties, than it would have been, if by the first grace the Christian had been made perfect.”

Thomas Boston, The Whole Works of Thomas Boston: Sermons and Discourses on Several Important Subjects in Divinity, ed. Samuel M‘Millan, vol. 6 (Aberdeen: George and Robert King, 1849), 124.

Rev. Shane Lems is a minister in the Orthodox Presbyterian Church and serves as pastor of Covenant Presbyterian Church in Hammond, Wis. This article appeared on his blog and is used with permission.