The mighty men of God, who throughout the centuries have wrought great things by prayer, are the men who have had much painful toil in prayer. Take for example, David Brainerd, that physically feeble, but spiritually mighty man of God. Trembling for years on the verge of consumption tuberculosis), from which he ultimately died at an early age, Brainerd felt led of God to labor among the North American Indians in the early days (1700’s), in the primeval forests of Northern Pennsylvania, and sometimes of a winter night he would go out into the forest and kneel in the cold snow when it was a foot deep and so labor with God in prayer that he would be wringing wet with perspiration even out in the cold winter night hours. And God heard David Brainerd, and sent such a mighty revival among the North American Indians as had never been heard of before, as indeed had never been dreamed about.
– R. A. Torrey –