I've been there, remember?
"I was answered that I must join none of them [Christian Churches], for they were all wrong...that all their creeds were an abomination in His sight."
Pearl of Great Price, Joseph Smith History 1:19
"I have learned for myself that Presbyterianism is not true."
Pearl of Great Price Joseph Smith History and History of the Church 1:6
"I spoke of the impropriety of turning away from the truth, and going after a people so destitute of righteousness as the Methodists."
Joseph Smith, History of the Church 2:319
"Behold there are save two churches only; the one is the Church of the Lamb of God and the other is the church of the devil; wherefore whoso belongeth not to the church of the lamb of God belongeth to that great church; which is the mother of abominations; and she is the harlot of all the earth."
Book of Mormon, 1 Nephi 14:10
"...orthodox Christian views of God are Pagan rather than Christian."
B. H. Roberts, Mormon Doctrine of Deity, p.116
"...all the priests who adhere to the sectarian religions of the day with all their followers, without one exception, receive their portion with the devil and his angels."
Joseph Smith Jr., editor, The Elders Journal, vol.1, no.4, p.60
ENDOWMENT AND SEALING PRECEDE SONSHIP.
The Lord has given unto us privileges, and blessings and the opportunity of entering into covenants, of accepting ordinances that pertain to our salvation beyond what is preached in the world; beyond the principles of faith in the Lord Jesus Christ, repentance from sin, and baptism for the remission of sins, and the laying on of hands for the gift of the Holy Ghost; and these principles and covenants are received nowhere else but in the temple of God.
If you would become a son or daughter of God and an heir of the kingdom, then you must go to the house of the Lord and receive blessings which there can be obtained and which cannot be obtained elsewhere; and you must keep those commandments and those covenants to the end. . .
Joseph Fielding Smith, Doctrines of Salvation, Vol. 2, p. 40
Many people think they need only confess that Jesus is the Christ and then they are saved by grace alone. We cannot be saved by grace alone, “for we know that it is by grace that we are saved, after all we can do.”
James E. Faust, “The Atonement: Our Greatest Hope,” October 2001 General Conference
Because of what He accomplished by His atoning sacrifice, Jesus Christ has the power to prescribe the conditions we must fulfill to qualify for the blessings of His Atonement. That is why we have commandments and ordinances. That is why we make covenants. That is how we qualify for the promised blessings. They all come through the mercy and grace of the Holy One of Israel, “after all we can do” (2 Nephi 25:23).
Dallin H. Oaks, “Two Lines of Communication,” October 2010 General Conference
http://www.lds.org/general-conference/2010/10/two-lines-of-communication?lang=eng
All of us have sinned and need to repent to fully pay our part of the debt. When we sincerely repent, the Savior’s magnificent Atonement pays the rest of that debt...
Many people think they need only confess that Jesus is the Christ and then they are saved by grace alone. We cannot be saved by grace alone, “for we know that it is by grace that we are saved, after all we can do.”
James E. Faust, “The Atonement: Our Greatest Hope,” October 2001 General Conference
http://www.lds.org/general-conference/2001/10/the-atonement-our-greatest-hope?lang=eng
"The Individual Effect of the Atonement makes it possible for any and every soul to obtain absolution from the effect of personal sins, through the mediation of Christ; but such saving intercession is to be invoked by individual effort as manifested through faith, repentance, and continued works of righteousness....The blessing of redemption from individual sins, while open for all to attain, is nevertheless conditioned on individual effort." - James Talmage, "A Study of the Articles of Faith" by (p. 89)
Sermons and Writings of Bruce R. McConkie, p.77 – “The blood of Christ was shed as a free gift of wondrous grace, but the Saints are cleansed by the blood after they keep the commandments.”
"The most fundamental purpose of your being on earth . . . is to prove yourself obedient to the commandments of the Lord and thereby grow in understanding, capacity, and every worthy trait. It is to receive every required ordinance and to make and keep every needed covenant. It is to form and nourish a family. This experience includes having periods of trial and happiness, with the objective of returning triumphantly, having met well the challenges and opportunities of mortal life to receive the glorious blessings promised for such obedience."
Richard G. Scott, "Truth Restored," Ensign, Nov. 2005, 78