From MormonWiki.org
"Man may commit certain grievous sins - according to his light and knowledge - that will place him beyond the reach of the atoning blood of Christ. If then he would be saved, he must make
sacrifice of his own life to atone - so far as the power lies - for that sin, for the blood of Christ alone under certain circumstances will not avail.
Joseph Smith taught that there were certain sins so grievous that man may commit, that they will place the transgressors beyond the power of the atonement of Christ. If these offenses are committed, then the blood of Christ will not cleanse them from their sins even though they repent. Therefore their only hope is to have
their blood shed to atone, as far as possible, in their behalf. This is scriptural doctrine, and is taught in all the standard works of the Church." -
Joseph Fielding Smith,
Doctrines of Salvation, v. 1, pp. 135-136, 1954
