Joseph Smith the Prophet taught: “As concerning the resurrection, I will merely say that all men will come from the grave as they lie down, whether old or young; there will not be ’added unto their stature one cubit, ’ neither taken from it; all will be raised by the power of God, having spirit in their bodies, and not blood.” (Teachings, pp. 199-200)
President Joseph F. Smith further explained: “The body will come forth as it is laid to rest, for there is no growth or development in the grave. As it is laid down, so will it arise, and changes to perfection will come by the law of restitution. But the spirit will continue to expand and develop, and the body, after the resurrection will develop to the full stature of man.” (Improvement Era, June 1904; cited in Teachings, p. 200, n. 4.)
By way of clarification, his son, Joseph Fielding Smith, observed:
“President Smith was in full accord with Amulek and Alma. He taught that the body will be restored as stated in Alma 11:42-45 and Alma 40:22-23. While he expresses the thought that the body will come forth as it was laid down, he also expresses the thought that it will take time to adjust the body from the condition of imperfections. This, of course, is reasonable, but at the same time the length of time to make these adjustments will not cover any appreciable extent of time. President Smith never intended to convey the thought that it would require weeks or months of time in order for the defects to be removed. These changes will come naturally, of course, but almost instantly.” (Doctrines of Salvation 2:293-94.)