Witsius against Perfectionsim

Witsius likened the remains of the flesh in the Christian life to the nations that Israel did not drive out of the land as reported in "Judges." God uses the remains of the flesh to test us and to train us. Witsius lists out a few reasons God allows the influence of the flesh in the Christians life:

But known to God are the reasons of his conduct, in dispensing the operations of the Spirit of grace in believers, so that the remains of the flesh are not entirely expelled in this life, For, 1st. He would by this, shew the difference between earth and heaven, the time of warfare and of triumph, the place of toil and of rest, that we may the more earnestly long for our translation out of this valley of sin and misery into the heavenly country, where every thing shall be made perfect; and may with open arms, embrace death, which will bring us to the perfection, crying out with the apostle; "O wretched man that I am, who shall deliver me form the body of this death?" Rom. vii.24.

The Economy of the Covenants Between God and Man Volume II by Herman Witsius (p. 47).