“The Work was born with the same naturalness with which a spring flows with water; because the water is there, it has to come forth. It is a supernatural phenomenon which we can’t explain humanly. The Lord chose me, a disproportionate instrument so that from the beginning it was clear that the Work is His.
“Some people ask about the theology which explains the birth and development of Opus Dei. They don’t realize that, when the Life-giving Spirit wants to raise up in the Church something new which breaks with the traditional – never totally because there is a chain from the apostolic period -, the first thing He does is establish the pastoral phenomenon, which can be full of a theology. In the case of the Work, it is a most delicate theology, an asceticism that is mystical because we unite action with contemplation in such a way that it’s possible to say that we are totally active and totally contemplative.
“Before provoking one of these pastoral phenomena, the Hierarchy of the Church and the person whom God has wanted to use to raise it up, must examine to see if the life and norm of this new phenomenon are in agreement with the Ecclesiastical Magisterium.
“Besides, it’s necessary to keep in mind that the repetition of acts produces the custom, and from there the juridical norm is born: the law has to proceed from the custom, from the lived pastoral phenomenon.
“The theory comes afterwards. You will write it after the years go by. You will be able to write magnificent treatises on the theology of Opus Dei, the asceticism of Opus Dei, the Mysticism of Opus Dei, the pastoral phenomenon of Opus Dei… You yourselves will write all of this. However, it is up to me to do it.
“To think differently is to be mistaken, to not understand how the works of God are born. To found any human society, cultural, sporting…a number of persons must come together, define the ends, look for plans… God acts in another way: first, He raises up the pastoral phenomenon, which leads one to live in a particular way. And when this life has the proper characteristics – because at times it does not have them because they are general – from there comes forth the theory, the theological reflection.”
After Life Comes Law
Motu Proprio Implementing Four Council Decrees
POPE PAUL VI August 6, 1966
“4. Moreover, to carry on special pastoral or missionary work for various regions or social groups which are in need of special assistance, prelatures composed of priests from the secular clergy equipped with special training can be usefully established by the Apostolic See. These prelatures are under the government of their own prelate and possess their own statutes.
It will be in the competence of this prelate to establish and direct a national or international seminary in which students are suitably instructed. The same prelate has the right to incardinate the same students and to promote them to sacred orders under the title of service for the prelature.
The prelate must make provision for the spiritual life of those whom he has ordained according to the above title, and for the continual perfecting of their special training and their special ministry making agreements with the local Ordinaries to whom the priests are sent. He must likewise provide for their proper support, a matter which must be provided for through the same agreements, either from the resources which belong to the prelature itself or from other suitable resources. In like manner he must provide for those who on account of poor health or for other causes must leave the task assigned to them.
Laymen, whether single or married, may also dedicate themselves with their professional skill to the service of these works and projects after making an agreement with the prelature.
Such prelatures are not erected unless the episcopal conferences of the territory in which they will render their services have been consulted. In rendering this service, diligent care is to be taken to safeguard the rights of local Ordinaries and close contacts with the same episcopal conferences are always to be maintained."
Opus Dei and the Aboriginal Church
I would dare to add that the connection between Opus Dei and the juridical figure of the prelature is not particular to Opus Dei. The transferral of Opus Dei from what I would call the "ligature" of the secular institute to the prelature simpy liberates Opus Dei to be what it really is: "a little bit of the Church," in the words of St. Josmaria Escriva. As Pedro Rodriguez remarked: "To think and speak of Opus Dei soon sends us back to what the Church essentially is, to its saving riches. All that Opus Dei is, it is within the mystery of the Church. Consequently, to study Opus Dei one needs to have a good grasp of ecclesiology. The better we understand the Church, the better will we see how the 'little bit' fits in" (P. Rodriguez, "The Place of Opus Dei in the Church" in Opus Dei in the Church Scepter  1.). And to make that specific, I would refer again to Rodriguez's observation to the "aboriginal relationship obtaining in the Church betrween christifideles - called to live out the requirements and implications of their baptism - and sacred ministers, who bring in, besides, the 'ministerial' consequences of the sacrament of Order" (Ibid. 38). Thus the Statutes of Opus Dei read: 'The ministerial priesthood of the clergy and the common priesthood of the lay people are so intimately linked that both, in unity of vocation and government, require and complement each other [ad invicem] in striving for the end proper to the prelature.'
"Thus, to the question, What is the ecclesiological nature of Opus Dei? one could reply: 'It is an institution whose internal structure replicates the basic ecclesial articulation between the common priesthood of the faithful possessed by the virtue of baptism, and the ministerial or hierarchical priesthood, possessed by the clerics incardinate in it.'
"So, what we find in Opus Dei, different yet complementing one another, are the two ecclesial forms of participating in Christ's priesthood. We find both the 'substantial' priority of Opus Dei's lay faithful, at whose service is the priestly ministry, and the 'functional' priority of the sacred ministry, in whose head [the prelate] resides the sacra potestas that governs the prelature. The clergy's 'functional' priority was described by the founder when he said that the ministerial priesthood 'impregnates with its spirit our personal life and all our apostolic work.' Opus Dei's Statutes put it more technically: 'Under the prelate's authority, the clergy, by means of their priestly minstry, enliven and inform all of Opus Dei.' But if these terms - inform, enliven - point to a 'functional priority,' they also clearly manifest the 'substantial priority' of Opus Dei's lay faithful. Graphically, the founder told the Work's priests that their task is to be a 'carpet' for others. He wrote: 'In Opus Dei we're all equal. There's only a practical difference: priests are more bound to place their hearts on the floor like a carpet, so that their brothers and sisters may tread softly' (Ibid. 38)."
 From St. Josemaria Escriva, Get-together with his sons on October 24, 1964.