E. M. Bounds 
Purpose In Prayer [EPUB ebook] 

The more praying there is in this world, the better the world will be, the mightier the forces against evil everywhere. Prayer, in one phase of its operation, is a disinfectant and a preventive. It purifies the air; it destroys the contagion of evil. Prayer is no fitful, short-lived thing. It is no voice crying unheard and unheeded in silence. It is a voice which goes into God’s ear, and it lives as long as God’s ear is open to holy pleas, as long as God’s heart is alive to holy things.Purpose in Prayer will awaken those who have neglected prayer, encourage those who desire help in this spiritual exercise, and give significant instruction to all who read its pages.