None of the devoted things shall stick to your hand, that the Lord may turn from the fierceness of his anger and show you mercy and have compassion on you and multiply you, as he swore to your fathers, Deuteronomy 13:17.
Israel must conquer idolatrous cities and destroy all the spoil, regarding all that had been polluted by idolatry as an accursed thing to be burned with fire. Now, sin of all sorts must be treated by Christians in the same manner. We must not allow a single evil habit to remain. It is now war to the knife with sins of all sorts and sizes, whether of the body, the mind, or the spirit. We do not look upon this giving up of evil as deserving mercy, but we regard it as a fruit of the grace of God, which we would on no account miss.
When God causes us to have no mercy on our sins, then He has great mercy on us. When we are angry with evil, God is no more angry with us. When we multiply our efforts against iniquity, the Lord multiplies our blessings. The way of peace, of growth, of safety, of joy in Christ Jesus will be found by following out these words: “There shall nought of the cursed thing cleave to thine hand.” Lord, purify me this day. Compassion, prosperity, increase, and joy will surely be given to those who put away sin with solemn resolution.
Charles H Spurgeon