Among the most authoritative documents which describe the Eucharistic miracle which took place at Gruaro in 1294 is that of local historian Antonio Nicoletti (1765). A woman was washing one of the altar linens of the Church of St. Giusto in the public wash house of Versiola. Suddenly she saw the altar linen become tinged with Blood. Observing more closely, she noted that the Blood was flowing from a consecrated Particle remaining among the folds of the cloth.
The relic of this miracle is kept in the Church of the Most Holy Body of Christ in Valvasone, but the miracle happened in Gruaruo. In 1294, a young housemaid went to the public wash-house of Versiola to wash the altar linens of the Church of St. Giusto in Gruaro. Suddenly, the woman noticed that a consecrated Host had remained by mistake among the folds of the cloth and that Blood was flowing from the Host.
Frightened by this inexplicable event, she immediately ran to alert the pastor who then informed the Bishop of Concordia, Giacomo di Ottonello from Cividade. The Bishop, having learned the facts, asked to be able to keep the cloth of the miracle in his Cathedral in Concordia. However, the pastor of Gruaro and the family of the Counts of Valvasone, patrons of the churches of Gruaro and of Valvasone, wanted to keep the cloth.
No agreement was reached, and so it was decided to seek recourse with the Holy See. In the end, Rome let the Counts keep the relic, on the condition that they would build a church dedicated to the Most Holy Body of Christ. The construction of the church was completed in 1483.