Perfect prayers are those which are inspired, in which the Spirit reveals the words which should be used. (3 Ne. 19:24.)
And if ye are purified and cleansed from all sin, ye shall ask whatsoever you will in the name of Jesus and it shall be done. But know this, it shall be given you what you shall ask.’
(D. & C. 50:29–30.).
(Bruce R. McConkie, Mormon Doctrine, p. 586)