Suppose you had a thousand-acre ranch and someone offered to buy it. You agree to sell the land except for one acre right in the center that you want to keep for yourself. In most parts of the country, the law would allow you to have access to that one lone spot by building a road across the surrounding property.
So it is with us as Christians if we make less than a full surrender to God. We can be sure that the devil will build roads to reach any uncommitted area of our life. When this happens, our testimony will be marred and our service will become ineffective.
Baker Books , 1500 Illustrations for Biblical Preaching, by Michael P. Green