On the rainy Thursday evening of August 21, 1879, at about 9 o'clock in the evening, at Knock Mhuire (County Mayo, Ireland), Mary McLoughlin, 45, and Mary Byrne, 29, saw a vision of the Virgin at the south gable of Knock Parish Church. Surprised, the women alerted several others in the village. Sixteen more people ran to the place and all of them saw the Virgin for nearly two hours. Those who left and later returned continued to witness the apparition.
The Virgin stood about two feet from the ground. She was clothed in white robes with a brilliant crown on her head. She was in an attitude of prayer. Saint Joseph and Saint John the Evangelist stood at her side. The witnesses also saw an "altar" with a lamb and a cross. Although the witnesses standing before the gable were drenched, no rain fell in the direction of the gable. The apparition was fully silent, and physical cures followed it.
On the altar, the sacrificial Lamb evokes the sacrifice of Calvary, made present every day during Mass. Saint John the Evangelist appeared as a priest, designating Mary present at the foot of the Cross given by Christ as his Mother to the disciple by the words: "Woman, behold, your Son." Each one of us is called to become a member of Christ, and to participate with him and Mary in the mystery of Redemption.