According to St. Sophronios of Jerusalem, who wrote the biography of St. Mary of Egypt, when she was about to enter the Church of the Holy Sepulcher on the feast of the Exaltation of the Honorable Cross, she was prevented from doing so by an invisible power due to her sinful intentions. After trying again and again to gain entry but failing, and seeing with what ease those around her entered, she looked up and saw an icon of the Theotokos and realized that it was her sins that prevented her from entering. Immediately she prayed to the Mother of God to allow her in and lead her by the hand on the path of repentance, promising that she would renounce the world and dedicate herself completely to Christ. Having fulfilled her promise, she became a model of repentance for centuries to pious Orthodox Christians.
At the southern tip of Mount Athos is the Cave of Saint Athanasios the Athonite, inside of which is believed to be, according to living Athonite tradition, the very icon of the Theotokos before which St. Mary of Egypt made her repentance. This icon is known as Panagia Eggyitria (Guarantor or Surety), and it was found in this cave by the founder of Athonite communal monasticism St. Athanasios himself around 965 A.D. Later he took the icon to Great Lavra Monastery so the fathers there could venerate it, but in the morning the icon disappeared and in a mysterious manner it was brought back to the Cave. St. Athanasios rediscovered the icon in the Cave and brought it back to his Monastery and placed it in the church, but again the next morning it was mysteriously found in the Cave. The miraculous icon was never again disturbed and has remained in the Cave ever since.
This holy icon is still under the care of Great Lavra Monastery and it is celebrated annually on the Saturday of the Akathist Hymn during the Fifth Week of Great Lent.
It is also beneficial to mention that in 1905 a catastrophic earthquake took place in the Halkidiki and Mount Athos peninsulas, causing massive damage to the monasteries, sketes and cells along with several casualties. During this time there lived in the Cave of Saint Athanasios the Athonite the famous Chariton the Spiritual Father (1836-1906) and his brotherhood. Just as Panagia Eggyitria guaranteed the salvation of the venerable Mary of Egypt, so also she did the same for the brotherhood that lived in asceticism in the Cave.
Elder Chariton had arranged one day to wake up a half hour earlier than usual and awaken the fathers to begin the morning Service. As soon as the earlier than usual Service began, the Cave began to shake and voluminous rocks were falling from high up with such a bang that it resembled a volcanic explosion. The rocks that fell crushed the part of the Cave where the cells of the fathers were and dragged it into the sea. But because the fathers began the Service early, they were spared of a sudden death and suffered no harm. As the morning dawned they completed the Service and left the church glorifying God and praising the Theotokos for their deliverance.
Meanwhile the fathers of Great Lavra Monastery thought the worst, and sent some fathers with animals and a Priest to see if anyone was spared from the earthquake, assuming there were no survivors. When they arrived at the Cave, not only did they find all the fathers safe and sound, but calm, even though they lost all of their belongings. Quite moved by this, they then heard the fathers speak about the miracle of Panagia Eggyitria, even though they were prepared to find them dead and chant for them a Funeral Service. So they departed glorifying God and the Theotokos, and just as with the venerable Mary of Egypt, so also today, the Panagia is the guarantor of salvation for all those who run to her protection with piety and faith.
It should be noted that according to St. Symeon of Thessaloniki, the icon of the Theotokos before which St. Mary of Egypt made a vow to enter the the desert was located in the narthex of Hagia Sophia in Constantinople to the right side of the imperial doors leading to the nave. On solemn occasions the patriarch venerated this icon before entering the nave of the Great Church to conduct services. Nearby was an icon of St. Mary of Egypt. The dowel holes where this icon probably was hung can still be seen today. On the left side was likewise an icon of Christ. Since the narthex was the place for catechumens and unrepentant sinners and Christians under penance, this would be the right place for this icon. Whether this was the actual icon before which St. Mary of Egypt prayed or it became symbolically associated is not known, and whether or not this icon is the same as that in Great Lavra Monastery is also not known, but it was still in Constantinople in the 14th century according to witnesses.