Parley P. Pratt provides scriptural arguments for polygamy.
Parley P. Pratt, Scriptural Evidences in Support of Polygamy (San Francisco: George Q. Cannon, 1856), 4–5, 9–10, 17–18
But though we cite the testimony of the Scriptures to convince, mankind that this principle was correct, and this institution was the one which the Lord revealed and even commanded his people in former, generations to observe, yet it is not upon this evidence that we presume to practice it at the present time. These scriptural evidences show what, the mind of the Lord was in former times relative to this principle; they show that the Latter-Day Saints in putting this doctrine in practice, merely do what the people of God did in previous ages, and therefore, that Polygamy is not a new-fangled doctrine of their own invention; but they do not give to the Latter-Day Saints, or to any other people, the right and authority to enter into the practice of this system aside from the command of God, any more than the Scriptures give the right and authority to every person who may peruse them to go forth and preach the gospel or officiate in its ordinances. Whenever this system is practiced under the divine sanction of the Almighty, it will be by His direct command; and He will undoubtedly reveal the laws by which its observance will be governed, so that everything connected therewith will be under proper restrictions and done in order. Until this command was given, though they had all the evidences of Scripture that this doctrine was believed and practiced by the people of God in ancient days, the Latter-Day Saints never dared to adopt it. The Lord in his wisdom, however, saw fit to give it, accompanying it by so strong a testimony of His Holy Spirit that there was no room to doubt; the only alternative that was left us, therefore, was to believe and obey it.
. . .
In the precedents recorded of Abraham and his posterity, two principles are conspicuous as being subservient to the carrying out of those ends: viz:
First: A plurality of wives:
Secondly: An entire prohibition of all sexual intercourse except upon the principle of marriage; — a breach of which was considered a capital offence, punishable with death. God provided Abraham with Sarah, Hagar, Keturah, and several other wives not named. By this means he became the father of many nations and his seed was multiplied exceedingly.
God also gave to Jacob, Abraham's grandson, four wives: viz; Leah, Rachel, Bilhah, and Zilpha; by which means he became the father of the twelve tribes. The history of these things is so conspicuous in the book of Genesis that we need not quote chapter and verse.
Now after Abraham had obtained all these wives, and had raised np children by them, the Lord bears testimony in the 26th chapter of Genesis, verse 5th, saying: "Abraham obeyed my voice and kept my charge, my commandments, my statutes,, and my laws." Here then, we have demonstrated that a man living four hundred years before the law of Moses was given, had statutes, commandments, and laws given to him of God; and that he kept them.
These laws evidently included polygamy or plurality of wives, from the fact that he had them, as a means of earning out the promise of exceeding multiplicity. Here then, the matter is set forever at rest, that polygamy is included in the ordinance of marriage, and in the everlasting covenant and laws of God; and that, under proper regulations, it is an institution holy, just, virtuous, pure, and, in the estimation of God, abundantly calculated to bless, preserve, aud multiply a nation. Hence the laws of some of our States, which recognize polygamy as a crime, are at once both unscriptural, and unconstitutional, as well as immoral. Common law in England, and in the United States, recognizes the Bible as the very foundation of all moral and criminal jurisprudence; and the Constitution of the United States, and of each State guarantees the liberty, of at least an enlightened conscience, founded on the moral law of God as found in that Holy Book. Hence, should an individual, or a community, in all good faith regulate their marriages by the laws of God as given to Abraham, no State law can harm them while the civil courts are bound to abide that holy and sacred guarantee of the Constitution: viz: "-Liberty of Conscience."
. . .
Thus the laws of modern "Christendom," borrowed from Rome, have overwhelmed the nations with the grossest immoralities — with sin, and sorrow, and tears, and wretched loneliness and widowhood. The widows mourn having no husbands; the virgins mourn having no bridegrooms; children mourn having no protectors; and families and nations mourn, having no confidence in themselves or each other. Virtue and confidence have fled; mercy weeps tears of blood; charity itself falters, and is ready to yield to the cries of justice for vengeance on the earth.
What, then, shall the righteous do?
"We reply: Restore the law of God — the new and everlasting covenant. Let every good citizen of both sexes marry at a proper age: bless them, and say: "Be fruitful and multiply." Make death the penalty for fornication and adultery: thus throwing a shield around our families and sacred domestic institutions. Let the monogamic law, restricting a man to one wife, with all its attendant train of whoredoms, intrigues, seductions, wretched and lonely single life, hatred, envy, jealousy, infanticide, illegitimacy, disease and death, like the millstone cast into the depths of the sea, sink with great Babylon to rise no more. Let every man and woman be virtuous, pure, holy, filling the measure of their creation. And let us go to, and fill these mountains; the States, North and South America; the earth; and an endless succession of worlds with a holy, virtuous, and highly intellectual seed; whose hearts shall delight in the law of God.
Let our sons become the sons of God, through faith in Jesus Christ, and obedience to the gospel; let this law be indelibly engraved on the tablet of their hearts: let them be early indoctrinated in every principle of virtue and honor: that each may be a conservatory of chastity, and wield a savory influence in every circle of his acquaintance. Let them learn to respect themselves as sons of God, and the other sex as sisters, daughters of the Highest, holy vessels, eternal beings, destined as companions and co-workers in the great science of life. Let them be taught to aspire, by every principle of honor and integrity, to the patriarchal throne, as heads of families and saviours of men.
Let our daughters also obey the ordinances of God, and receive and cultivate the gift of the Holy Ghost, in every good and pure affection. Let them early understand the true relationship they are destined to sustain to the other sex. Let them be taught to respect them as brothers, worthy of their confidence and affection, worthy to become their savior, and head, as Christ is the head of the church. Let them be taught to respect and revere themselves, as holy vessels, destined to sustain and magnify the eternal and sacred relationship of wife and mother: to be the ornament and glory of man; and to share with him a never fading crown, and an eternally increasing dominion.
In short, let us educate our sons and daughters in all that is holy and true, and virtuous and pure, and lovely and of good report: let us gradually and carefully develop in them the true affections and attributes of their nature: let us cultivate every intellectual and moral sense and faculty within them, and lead them gently onward in the great science of life and exaltation; that, when time shall be no more, we may rejoice with the untold millions of our posterity in the eternal mansions.