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 own 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.