1) Historical text: “Only rarely did the Father [St. Josemaria Escriva] mention these supernatural events; he would not do it unless he considered it necessary for the good of the Work and of his children. So we know little about the extraordinary graces that he received. But we do know some of them: for instance, that of August 23, 1971. He was spending a few days in Caglio, a little village near the town of Como, in northern Italy. That morning, after celebrating Mass, he was reading the newspaper, and suddenly, with great clarity and irresistible force, there was imparted to his soul a divine locution: `Adeamus cum fiducia ad thronum gloriae, ut misericordiam consequamur’ (`Let us confidently approach the throne of glory, to obtain mercy’).
Then, the footnote: “This is Hebrews 4, 16, with one difference: `throne of glory,’ instead of `throne of grace.’ The founder explained that our Lady is the throne of glory, in virtue of her constant and unalloyed intimacy with the Father, the Son, and the Holy Spirit. It is good that by means of her intercession we betake ourselves to God, appealing humbly to his mercy… The founder was in the habit of doing that, and so this locution `confirmed him in his need to always go to her’… He directed Don Alvaro to communicate this locution, in writing, to those on the General Council; this was, Ernesto Julia testifies, the only occasion on which he proceeded in this way…
Archbishop [now Cardinal] Julian Herranz tells us something interesting. He heard about this supernatural incident from the founder himself, shortly after the return from Caglio. At this time the work on Cavabianca (the definitive seat of the Roman College of the Holy Cross) had already begun, and the Father asked that they put there a stone bas-relief which would show our Lady seated on a throne and being crowned oby the Blessed Trinity. AT its base would be engraved the words of the locution. The Father suggested that while they awaited the juridical solution to the institutional problem of the Work, those words should be prayed as an aspiration, to obtain from our Lady the desired solution. That was a suggestion that his children acted on for years. `And so,’ concludes Archbishop Herrance, `very great were our joy and our gratitude to the Blessed Virgin when the Pope (who knew nothing about this) made public his decision to establish Opus Dei as a personal prelature on August 23, 1982 – the anniversary of the special divine light received by the founder eleven years earlier.’”
2) The communication of the locution by St. Josemaria himself.
“I am going to tell you something that God Our Lord wants you to know. The sons of God in Opus Dei adeamus cum fiducia - we must go with much faith – ad thronum gloriae, to the throne of glory, the Most Holy Virgin, the Mother of God and our Mother, whom we invoke so many times as Sedes Sapientiae, ut misericordiam consequamur, to get mercy…
“Keep it in mind in these moments and also afterwards. I would say that it is a desire of God: that we place our personal interior life within these words that I have just said. At times you will hear them without the noise of words, in the intimacy of your soul, when you least expect it. Adeamus cum fiducia: go – I repeat – with trust to the most Sweet Heart of Mary, who is our Mother and Mother of Jesus. And with Her, who is Mediatrix of all grace, to the Most Sacred and Merciful Heart of Jesus Christ.”
3) Historical Account of the Erection of the Prelature:
On August 23 of 1982, the Holy Father, John Paul II, made the official announcement of his decision to erect Opus Dei as personal Prelature after having approved – on the 5th of August of 1982, feast of our Lady of the Snows – a Declaration of the Sacred Congregation for Bishop in which the fundamental characteristics of the new Prelature are explained. Finally, the Holy Father ordered the Prelature to be erected on the 28th of November of 1982, the first Sunday of Advent. He ordered the pontifical act be published on that Sunday’s vigil, that is, the afternoon of Saturday November 27th which coincided with a date beloved by St. Josemaria, the feast of the Virgin of the Miraculous Medal, which was also the anniversary of the death of his Father.
 Andres Vazquez de Prada, The Founder of Opus Dei Scepter (2004) 426-427.