On Friday, June 5, 1405, the chaplain of the small fortified chapel of Bois-Seigneur-Isaac — Father Pierre Ost — opened the corporal after Mass to find it suddenly saturated with red, fresh blood. According to his sworn deposition, simultaneously a vision of Christ wounded and bleeding appeared above the altar, identifying itself: 'I am the King of Glory, who suffered for the salvation of the world.'
Bishop Pierre d'Ailly of Cambrai opened a formal inquiry within months; the relic was preserved. Pope Martin V (at the Council of Constance) approved the public cult in 1428. The bloodstained corporal is still venerated in the Priory church of Bois-Seigneur-Isaac, now a quiet rural shrine in Walloon Brabant; an annual procession on the Monday after Trinity Sunday continues. The shrine is also linked to St. Pierre-Julien Eymard and the Blessed Sacrament Fathers, who served it in the 19th century.