And the Lord spoke to Moses, saying "Speak to all the congregation of the children of Israel, and say to them: 'You shall be holy, for I the Lord your God am holy.'"
No one whose senses have been exercised to know good and evil but must grieve over the sight of zealous souls seeking to be filled with the Holy Spirit while they are yet living in a state of moral carelessness or borderline sin. Such a thing is a moral contradiction. Whoever would be filled and indwelt by the Spirit should first judge his life for any hidden iniquities; he should courageously expel from his heart everything which is out of accord with the character of God as revealed by the Holy Scriptures.
At the base of all true Christian experience must lie a sound and sane morality. No joys are valid, no delights legitimate where sin is allowed to live in life or conduct. No transgression of pure righteousness dare excuse itself on the ground of superior religious experience. To seek high emotional states while living in sin is to throw our whole life open to self deception and the judgment of God. "Be ye holy" is not a mere motto to be framed and hung on the wall. It is a serious commandment from the Lord of the whole earth. The Pursuit of Man, 102.
And some more!
Spiritual Warfare and Sin: Fight or Die
For all that is in the world--the lust of the flesh, the lust of the eyes, and the pride of life--is not of the Father but is of the world. And the world is passing away, and the lust of it; but he who does the will of God abides forever. --1 John 2:16-17
Someday the church can relax her guard, call her watchmen down from the wall and live in safety and peace; but not yet, not yet....
The healthiest man has enough lethal bacteria in him to kill him within twenty-four hours except for one thing-the amazing power of the human organism to resist bacterial attack. Every mortal body must fight its internal enemies day and night. Once it surrenders its hours are numbered. Quite literally it must fight or die....
The church lives in a hostile world. Within and around her are enemies that not only could destroy her, but are meant to and will unless she resists force with yet greater force. The Christian would collapse from sheer external pressure were there not within him a counterpressure sufficiently great to prevent it. The power of the Holy Spirit is, therefore, not optional but necessary. Without it the children of God simply cannot live the life of heaven on earth. The hindrances are too many and too effective. That Incredible Christian, 86-87.