Marriage love does not occur between people of different religions, either, because the truth of one is not in harmony with the good of the other, and two unlike and discordant entities cannot make one mind out of two. This means that the source of their love has nothing spiritual in it. If they do live together in harmony, it is strictly for natural reasons.
For this reason, marriages in the heavens are contracted with people within their own community because they are focused on similar kinds of good and truth, and they do not associate with people outside their community. It may be seen in Sections 41–45 that all the people who are within a given community are focused on similar good and truth, and that they differ from people who are outside the community. This was also represented in the Israelite nation by the fact that they contracted marriages within their tribes and even within their clans, and not outside them.
Genuine marriage love is not possible between one husband and more than one wife. Polygamy in fact destroys the spiritual source of marriage love, whose purpose is to form one mind out of two. It therefore destroys the deeper union of the good and the true that is the very essence of that love. Marriage with more than one is like an intellect divided among more than one will or like a person pledged to more than one church. This actually pulls faith apart so that it becomes no faith at all.
Angels say that taking more than one wife is absolutely contrary to the divine design and that they know this for many reasons, including the fact that the moment they think about marriage with more than one, they are estranged from their inner blessedness and heavenly happiness. They become virtually drunk because the good is severed from the true within them; and since the deeper levels of their minds come into this kind of state when they simply think about this with some slight intent, they perceive clearly that marriage with more than one woman closes their own inner nature and makes lust invade where there should be marriage love. Lust leads away from heaven.
They added that people on earth have a hard time understanding this because so few do experience true marriage love, and if people are not intent on this, they have absolutely no knowledge of the inner delight that dwells within that love. They are aware only of the delight of lust, a delight that turns disagreeable after people have lived together for a little while. The delight of real marriage love, though, not only lasts into old age on earth but even becomes heavenly delight after death, when it is filled with a deeper delight that becomes better and better to eternity.
The angels even said that the blessings of real marriage love could be listed in the thousands, with not a single one known to people here or comprehensible to the understanding of anyone who is not in a marriage of the good and the true from the Lord.
from Heaven and Hell, Sections 378, 379
Sections 41-45: See 5/7/2017 and 5/8/2017