Isaiah 1:18
"though you sins be as scarlet, they shall be white as snow"
Alma 26:22
"Yea, he that repenteth and exerciseth faith, and bringeth forth good works, and prayeth continually without ceasing—unto such it is given to know the mysteries of God; yea, unto such it shall be given to reveal things which never have been revealed; yea, and it shall be given unto such to bring thousands of souls to repentance, even as it has been given unto us to bring these our brethren to repentance."
Alma 34:30-35
"...come forth and bring fruit unto repentance."
"Yea, I would that ye would come forth and harden not your hearts any longer; for behold, now is the time and the day of your salvation; and therefore, if ye will repent and harden not your hearts, immediately shall the great plan of redemption be brought about unto you."
"I beseech of you that ye do not procrastinate the day of your repentance until the end."
"that same spirit which doth possess your bodies at the time that ye go out of this life, that same spirit will have power to possess your body in that eternal world."
Moroni 8:25-26
"the remission of sins bringeth meekness, and lowliness of heart; and because of meekness and lowliness of heart cometh the visitation of the Holy Ghost, which Comforter filleth with hope and perfect love, which love endureth by diligence unto prayer..."
D&C 19:15-20
"For behold, I, God, have suffered these things for all, that they might not suffer if they would repent"
"I command you again to repent, lest I humble you with my almighty power; and that you confess your sins, lest you suffer these punishments of which I have spoken..."
D&C 58:42-43
"Behold, he who has repented of his sins, the same is forgiven, and I, the Lord, remember them no more."
I love Isaiah 1:18 because the analogy of sin being red and repentance turning them white shows how we can be cleansed spiritually. Sin weighs us down, makes us feel burdened, and hampers our ability to feel the spirit. When we go through the proper steps of repentance- covenanting to not do it again, making restitution, studying, and forgiving ourselves- we can feel those burdens being lifted and the return of the Holy Ghost. The time to repent is NOW. If we don't repent now, the same spirit carries with us when we die.