“Prayer will consume sin, or sin will choke prayer.”

“Prayer will make a man cease from sin, or sin will entice a man to cease from prayer.”

“Prayer busters (causes of unanswered prayer) are prayerlessness, unconfessed sin, unresolved relational conflict, selfishness, uncaring attitudes, and inadequate faith.”

“Sin is anti-will to God's will; it sets itself to oppose preaching, prayer, and all the institutions of God.”

“The sin that now rises to memory as your bosom sin, let this first of all be withstood and mastered. Oppose it instantly by a detestation of it, by a firm will to conquer it, by reflection, by reason, and by prayer.”

“If you're tolerating sin in your life, my friend, don't waste your breath praying unless it's a prayer of confession.”

“There was purification in punishment. Not 'Forgive us our sins,' but 'Smite us for our iniquities' should be the prayer of a man to a most just God.”

“Gay, guiltless pair,
What seek ye from the fields of heaven?
Ye have no need of prayer,
Ye have no sins to be forgiven.”

“If you let even a little sin into your heart, it's going to contaminate your prayers. Your Christian life will not achieve its full potential.”

“It is certain that men’s prayers are more pleasing to God if they go up to Him from a pure heart; from souls, that is, that are free from all sin.”