Brigham says that only those faithful to their priesthood can enter plural marriage.
Brigham Young, "Plurality of Wives," Journal of Discourses, 19 vols. (Liverpool: Orson Pratt, 1856), 3:265
The Lord has instituted this plan for a holy purpose, and not with a design to afflict or distress the people; hence, an important and imperative duty is placed upon all holy men and women, and the reward will follow, for it is said, that the children will add to our honor and glory.
It hurts my feelings when I see good men, men who love correct principles and cling to the counsels of the Church, who have lived near to God for years and have always been faithful, with not a child to bear up their names to future generations, and I grieve to reflect that their names must go into the grave with them.
It would please me to see good men and women have families; I would like to have righteous men take more wives and raise up holy children. Some say, "I would do so, but brother Joseph and brother Brigham have never told me to do it."
This law was never given of the Lord for any but his faithful children; it is not for the ungodly at all; no man has a right to a wife, or wives, unless he honors his Priesthood and magnifies his calling before God.
I foresaw, when Joseph first made known this doctrine, that it would be a trial, and a source of great care and anxiety to the brethren, and what of that? We are to gird up our loins and fulfil this, just as we would any other duty. (High wind and clouds of dust prevented speaking for several seconds.)
It has been strenuously urged by many, that this doctrine was introduced through lust, but that is a gross misrepresentation. (A thick cloud of dust prevented speaking for about two minutes.)
This revelation, which God gave to Joseph, was for the express purpose of providing a channel for the organization of tabernacles, for those spirits to occupy who have been reserved to come forth in the kingdom of God, and that they might not be obliged to take tabernacles out of the kingdom of God.