That is until Tuesday after Pentecost, the Blood continued to flow, reaching the length of a finger in three breadths. Then, having stained the entire corporal, the Blood co-agulated little by little and dried up. The miracle was seen and attested to by many. The Bishop of Cambrai, Peter d' Ailly, was informed of what happened and he decided to investigate personally and had the corporal in his care for some two years. Every attempt to remove the stains of Blood on the corporal were useless.
For four days, the Bishop opened an investigation where testimonies were gathered regarding the prodigies wrought by the reliquary of the precious Blood. On June 16, 1410, the Bishop granted an indulgence of 40 days to those who visited the Chapel at Bois-Seigneur-Isaac. On May 3, 1413, he allowed the corporal to be venerated as a relic and established a solemn procession in honor of the miracle, along with public exposition of the Blessed Sacrament. Even today, every year on the Sunday following the Feast of the Birth of Mary, the citizens of Bois-Seigneur-Isaac come together in prayer to celebrate the memory of this Eucharistic miracle.