Announcing his retirement in February, Pope Emeritus Benedict XVI took 1.3 billion Roman Catholics worldwide by surprise, becoming the first pontiff to step down voluntarily since Gregory XII in 1415.

The first question that sprang to the minds of many was, why.

Now the Catholic news service Zenit is reporting that told a visitor he resigned in March because "God had told me."

The unnamed visitor met with the retired pope several weeks ago at his residence at Mater Ecclesia monastery, where he now lives. Benedict clarified that he did not encounter an apparition or some other phenomenon of that kind.

Instead, the Pope Emeritus said it was more a "mystical experience."

The anonymous source said that this experience has continued more and more for the man who rose to become Pope after serving as a cardinal. It has the former Joseph Ratzinger longing for a deeper relationship with God.

The former pope said that God had given him an "absolute desire" to be alone with him.

This recent report does not tie in entirely with earlier statements by Benedict. In February he cited his lack of strength and health due to his increased age.

However, Vatican sources said the Zenit article is accurate Britain's Telegraph newspaper reported.

"The report is reliable, without a doubt, although this is not an official Vatican statement or position," one source said.

Zenit reporter Salvatore Cernuzio wrote, "Now more than six months after the announcement that shook the world, Benedict's decision to live a hidden life is still being reflected upon.

"Some have had the privilege to listen to the Pope Emeritus himself speak about his choice. Despite his cloistered life, Benedict has allowed—sporadically and only on certain occasions—some private visits at Mater Ecclesiae."

Although some had thought that his retirement and the election of Pope Francis might produce tension, the two reportedly get along quite well.

Benedict said the more he observes the "charisma" of the new pope, he believes that his selection was the "will of God."

The UK's Guardian newspaper reported that Francis has even joked about the situation, saying in July: "The last time there were two or three popes, they didn't talk among themselves and they fought over who was the true pope!"

Having Benedict living in the Vatican, he added, "is like having a grandfather – a wise grandfather – living at home".

Furthermore, the Vatican Insider said this week in an article about Benedict's remarks that in an earlier interview with a German academic, the Pope Emeritus indicated that he and Francis were in tune theologically.

The independent news source also noted that "Francis never misses a chance to publicly praise his predecessor, whose advice he treasures."