Brickmore discusses how Christian marriage was referred to by Paul as "a great mystery" in itself, which also symbolized the union of Christ and the Church. He quotes early Church Father, Justin Martyr and how he not only defended the polygamy of Old Testament figures, but referred to it as a "mystery" as well:
"And this one fall of David, in the matter of Uriah's wife, proves, sirs," I said, "that the patriarchs had many wives, not to commit fornication, but that a certain dispensation and all "mysteries" might be accomplished by them; since, if it were allowable to take any wife, or as many wives as one chooses, and how he chooses, which the men of your nation do over all the earth, wherever they sojourn, or wherever they have been sent, taking women under the name of marriage, much more would David have been permitted to do this." (Justin Martyr, Dialogue With Trypho 141, in ANF 1:270.)Brickmore explains how the evidence is not conclusive, yet a form of plural marriage may have been practiced by some of the Apostles and prophets in the early Church. In an early Christian text called, "The Didache," also known by two other titles, "The Teaching of the Twelve Apostles" and "The Lord's Teachings to the Gentiles by the Twelve Apostles," it speaks about prophets who "work unto the "mystery of the church," which "mystery" he maintains was "seen as marriage--and possibly even plural marriage."
"And every prophet, proved true, working unto the "mystery of the Church" in the world, yet not teaching others to do what he himself doeth, shall not be judged among you, for with God he hath his judgment; for so did also the ancient prophets." (Didache 11, in ANF 7:380-381.)
In 'Early Christian writings: the Apostolic Fathers' we are told: "This passage is very obscure; it may mean that prophets may perform "symbolic actions" as the prophets of the Old Testament did (an extreme example would be Hosea’s marriage to a cultic prostitute); the "cosmic mystery of the Church" (translated in the text as "the mystery of the Church in the world") which the prophet lives may, however, mean celibacy, or even a "spiritual marriage" between a prophet and his (female) companion."(Early Christian writings: the Apostolic Fathers; Andrew Louth, Maxwell Staniforth; note 9; pg 198.)
The footnote (523) for this verse states: "Literally, "acts with a view to a worldly "mystery" of the Church." The meaning is not certain, but some dramatic action, symbolizing the "mystical marriage" of the Church to Christ, is probably intended. The reference may, indeed, be to the prophet's being accompanied by a "spiritual sister." (cf. I Cor. 7:36ff.)
Also, the first part of that quote, "every prophet, proved true" seems to speak to a type of test perhaps in much the same way Abraham had been tested by God. Yet not only Abraham but also the other "ancient prophets" to see if they would do all that the Lord had commanded them.
Brickmore goes on to explain how Cardinal Jean Daniélou in his book, 'The Theology of Jewish Christianity' linked this "mystery" to the type of "spiritual marriages" that groups like the Marcosians practiced:
The expression "cosmic mystery of the Church" seems to stand in opposition to a "heavenly mystery of the church." This heavenly "mystery" is the "celestial marriage" of Christ to the Church, which also finds its expression in this world. The allusion in this passage would therefore seem to be to those "spiritual unions" which existed in Jewish Christianity between prophet-Apostles and a sister. Hermas also appears to allude to this custom (Sim. IX, 10:6-11:8). A similar reference may underlie I Cor. 7:36ff. The custom endured in the institution of Virgins. The relation of these unions to their heavenly ideal is explicitly stated by the Gnostics: "Some of them prepare a nuptial couch and perform a sort of mystic rite (mystagogia-pronouncing certain expressions) with those who are being initiated, affirming that what is performed by them is a "spiritual marriage" which is celebrated by them, after the likeness of the unions…above" (Irenaeus, Against Heresies 1:21:3, in ANF 1:346.). (Daniélou, The Theology of Jewish Christianity, p. 351.)
The Gnostic rite is described in the Gospel of Philip as being performed in "the mirrored bridal chamber," and "those who have united in the bridal chamber will no longer be separated." (The Gospel of Philip, in James M. Robinson, ed., The Nag Hammadi Library in English, 139 & 142.)
Stuart George Hall writes that Melito, Bishop of Sardis in the late second century, may have preserved a fragment of the ancient bridal chamber ceremony in his writings, as well (Stuart George Hall, ed., Melito of Sardis On Pascha and Fragments (Oxford: Clarendon Press, 1979), xxxviii.).
Brickmore also explains how Daniélou saw no connection with plural marriage yet he found that it is evident that this "mystery" was something that the "ancient prophets" practiced, but which was forbidden for ordinary Christians. Considering Paul's prohibition against plural marriage for bishops and deacons, it may well have been polygamy."
In Did.11:11 the prophetic performance of a “cosmic mystery of the church” is regarded by a majority of commentators, following A.Harnack, as the enactment of a “spiritual marriage” by the prophets (H. Weinel, Die Wirkungen des Geistes, pp. 131-38.)
A question might also be raised that if the early Christians did not practice polygamy then why would Paul have a prohibition against it just for bishops and deacons and not for others such as prophets? In another post it has been shown that 'one' wife may also mean 'first' wife, in that bishops and deacons needed to be upstanding and ones who were married to their 'first' wife were deemed worthy....as there would be no bill of divorcement. We learn from the Diadache about early Christian prophets and how to know a true prophet from a false prophet. Particular immunity or liberty allowed true prophets are emphasized in Didache 108; 117, 11.
Peter explained the same principle to the apostate Simon Magus in the Clementine Homilies:
There is not much written on the mysteries as the early Christians were under an oath to keep them secret. Peter, in Clementine Recognitions said: "We remember that our Lord and Teacher, commanding us, said, 'Keep the "mysteries" for me and the sons of my house.' Wherefore also He explained to His disciples privately the mysteries of the kingdom of heaven. But to you who do battle with us, and examine into nothing else but our statements, whether they be true or false, it would be impious to state the hidden truths." (Clementine Homilies 19:20, in ANF 8:336. "For the most sublime truths are best honored by means of silence." Peter, in Clementine Recognitions 1:23, in ANF 8:83.)
Robert M. Grant notes that, "In Ephesians 5:22-33 the prophecy of Genesis 2:24 {'the two shall become one flesh.'} is described as "a great mystery" and is referred not only to Christ and the church but also to Christian marriage in general." (Robert M. Grant, After the New Testament (Philadelphia: Fortress Press, 1967), 184.)
At The Birth of the Catholic Church, Ch.X 1. The Christian Prophets we are told:
...the Didache forbids the reception of any preacher who teaches a doctrine contrary to the catechesis just developed in the book (xi, 1-2) which, be it remembered, is almost entirely moral and ritual, like the Christianity described in Pliny's letter to Trajan. The Didache knows moreover of travelling apostles and of prophets who remain at home in one place. Travelling apostles who stay more than two days, in order to get more board and lodging, or ask for money, are to be reckoned false (xi, 3-6), and this, not so much on account of their heresies, but on the moral ground that they are exploiting their hosts, though possibly heretical as well as rapacious. As to the sedentary prophets, their inspired outpourings are not to be lightly criticized, but conduct is to be the test for distinguishing the true prophet from the false. He alone is a true prophet who lives according to the Lord....The prophets of old had certain eccentricities, and a few such, analogous to theirs, and "in harmony with the cosmic mystery of the Church," may be tolerated in Christian prophets, provided they do not require others to imitate them (xi, n). A highly enigmatic concession, at least for us, and sufficiently disturbing in itself; it cannot have been maintained for long. (The ancient prophets are brought in only by way of a mitigating comparison.) The reference is to some symbolic proceedings representing "the mystery," which is, one can hardly doubt, the mystic union of the Christ and "the Church." According to Irenaeus the innocent "conjunctions" (syzygies) of Valentinus seem to have been mixed up by his disciple Marcus with certain rites of symbolic magic in which mysticism had degenerated into eroticism. What the Didache had in mind must have been something less abominable, perhaps a symbolic marriage between an inspired couple, which may have been real, or an affair of continency (refraining from sexual intercourse) on both sides. But we can see that the author of the Didache, while not daring to prohibit these eccentricities, is not quite at ease in the matter."Spiritual marriage" has sometimes assumed a questionable form, in which a early Christian holy men would take laywoman as a wife, claim to remain celibate, and claim that they slept in the same bed but did not engage in sexual relations as a sign of their own willpower. Most, however, doubted that they were in fact as strong in chastity as they claimed. However, the testing of spirits, once commended by Paul (1 Thess. 5:21), might be a matter of delicacy. So the Didache exempts from human scrutiny a prophet who "acts out a "cosmic mystery of the Church," and then does not teach others to do what he has done." To question their oracles was to sin against the Holy Ghost.
