James Duncan, preaching with great unction and power, was asked what was the secret of such powerful preaching. "The secret," he said, was "thirteen hours of consecutive prayer."

When asked the secret of his spiritual power, Charles Spurgeon said: "Knee work! Knee work!"

Livingston of Shotts, on two different occasions, preached with such power that in each service 500 were converted. Both sermons were preceded by a night of prayer.

Charles Finney, after spending a day in the woods in prayer and fasting, preached that night in a phenomenally irreligious congregation. The sermon was accompanied by such divine power that the whole congregation, except one man, fell prostrate upon the floor, and voiced their agony under conviction of sin, in such loud outcries that the preacher was forced to stop.

Of "Uncle" John Vassar, The Tract Society colporteur, his pastor says: "He absolutely prayed day and night prayed about everything, prayed for almost everything, prayed with almost everybody he met. He prayed when he went out and when he came in. He prayed before every religious service, and then prayed all the way through it. I have occupied the same room with him night after night, and rarely went to sleep without hearing him in prayer, or awoke without finding him in prayer."