Power Developed by Prayer and Fasting
21 Howbeit this kind goeth not out but by prayer and fasting.
Elder James E. Talmage wrote:
“The Savior’s statement concerning the evil spirit that the Apostles were unable to subdue—‘Howbeit this kind goeth not out but by prayer and fasting’—indicates gradation in the malignity and evil power of demons, and gradation also in the results of varying degrees of faith. The Apostles who failed on the occasion referred to had been able to cast out demons at other times. Fasting, when practiced in prudence, and genuine prayer are conducive to the development of faith with its accompanying power for good. Individual application of this principle may be made with profit. Have you some besetting weakness, some sinful indulgence that you have vainly tried to overcome? Like the malignant demon that Christ rebuked in the boy, your sin may be of a kind that goeth out only through prayer and fasting.”
(Jesus the Christ, 3rd ed. , 395.)