This verse is the key to gaining an insight into what the Nephites understood in regard to the practice of plural marriage. They knew, as do we, that monogamy was the rule, plural marriage the exception.
They knew that unless God commanded otherwise, a man was to have but one wife. But they also knew from the accounts of the Old Testament prophets and peoples, that God occasionally called upon his people to do otherwise, to “raise up seed unto” him through plural marriage.
The directive so to do, however, has never been independent of that order and discipline common to the Lord’s Church and kingdom-it has come through holy men of God, men holding the keys of such power (see D&C 132:39).
To the Saints in 1843 Joseph Smith said: “I hold the keys of this power in the last days; for there is never but one on earth at a time on whom the power and its keys are conferred; and I have constantly said no man shall have but one wife at a time, unless the Lord directs otherwise. ” (Teachings, p. 324; italics in original.)