It is interesting to note the symbols used here by the Savior to teach the sanctifying, cleansing power of the infinite and eternal sacrifice of the Lamb of God. How do sin-stained garments become pure white when immersed in the blood of Christ?
Mortal blood is a staining agent itself, but somehow, spiritually speaking, the blood spilled by a God in our behalf becomes the only true cleansing agent. We cannot cleanse our sin-stained lives by mere washing in the strong detergent of self-discipline. It requires a celestial cleanser, one which we cannot purchase for ourselves but is purchased for us by the grace of God—the blood of Christ.
“Nothing Entereth into His Rest Save It Be Those Who Have Washed Their Garments in My Blood”The “rest of the Lord” to which Jesus is referring in this verse undoubtedly is ultimate exaltation in the presence of God (see D&C 84:24), but other definitions of the phrase “rest of the Lord” would likewise apply. The rest of the Lord could be the earthly peace and spiritual rest from the tumult and turmoil of the soul. The righteous, meaning those whose garments have been made white in Christ’s blood, also enter the rest of the Lord at death when they enter paradise (see Alma 40:12; Alma 60:13). The cleansing power of the Atonement also enables a person to enter into the personal presence of the Savior, which too is the rest of the Lord (see JST, Exodus 34:1-2; D&C 67:10; D&C 88:68).