Joseph Fielding Smith
"Mark you, this word strait is spelled s-t-r-a-i-t and not s-t-r-a-i-g-h-t. While no doubt, that path which leads into the presence of God is straight, it is also strait, which means that those who enter into it will find it restricted; it is narrow; they cannot take with them that which does not apply, or which does not belong to the kingdom of God. All such things must be left behind when we enter into this narrow way which leads in to the presence of God, where we can receive life eternal. 'Few there be that find it.'" (Doctrines of Salvation, vol. 2. pp. 13-14 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p.31-2)
Bruce R. McConkie
"The course leading to eternal life is both strait and straight. It is straight because it has an invariable direction -- always it is the same. There are no diversions, crooked paths, or tangents leading to the kingdom of God. It is strait because it is narrow and restricted, a course where full obedience to the full law is required. Straightness has reference to direction, straitness to width. The gate is strait; the path is both strait and straight. (2 Ne. 9:41; 31:9, 17-18; 33:9; Alma 37:44-45; Hela. 3:29-30; 3 Ne. 14:13-14; 27:33; D. & C. 22; 132:22; Matt. 7:13-14; Luke 13:23-24; Heb. 12:13; Jer. 31:9.)
"Thus by entering in at the strait gate (which is repentance and baptism) a person gets on the 'straight and narrow path which leads to eternal life.' (2 Ne. 31:17-18.)" (Bruce R. McConkie, Mormon Doctrine, p. 769)