There was once a reservoir in the hills that supplied a village community with water. It was fed by a mountain stream, and the overflow of the reservoir continued down the streambed to the valley below. There was nothing remarkable about this stream--it seldom overflowed its banks or gave the villagers any trouble.
One day, however, some large cracks appeared in one of the walls of the reservoir. The wall collapsed and the waters burst down the hillside, destroying all the houses and bridges that lay in its path. The streambed could no longer contain the volume of water, and the overflow inundated the countryside. What had before been ignored or taken for granted now became an object of awe, wonder, and fear.
This is a fitting picture of revival. Often in the period just preceding this kind of breakthrough, the stream of divine power and blessing has seemed unusually low. The people of God and the work of God have been in great affliction and reproach, despised or ignored by those around them. In response, however, to the prayers of a burdened remnant, God has been quietly heaping the flood. Suddenly, when the majority has no expectation of it, God opens the windows of heaven and pours out his blessing in such abundance that the channels of organized religion cannot contain it.
The flood of life and blessing then becomes an object of awe and wonder. Works of darkness and strongholds of Satan that have long resisted the normal influences of the Spirit are swept away. Stubborn wills that have long withstood the overtures of the gospel and the pleadings and prayers of loved ones now bend and break before the irresistible flow of the Spirit, to be engulfed themselves and borne along in the stream of blessing.
Thus does God see fit to use revival to create spiritual momentum, to accomplish in days what could never otherwise be achieved in years of normal Christian activity. However, in our zeal for revival, we must not disparage what is achieved in the quieter seasons for God has His purposes in these times also. The patrolling and the harassing and the limited advances are all essential to the big offensive. “The day of small things” (Zechariah 4:10) is preparatory and supplementary to “the day of [God’s] power” (Psalm 110:3), and we must not despise it.
Arthur Wallis : The Purpose of Revival (Part I)