St Anthony is known for his profound love for people and his sympathy for those in disbelief. He believed they deprived themselves of the Sacraments especially the Eucharist which he held dear to his heart. The Saint was so attached to this spiritual food that he considered being away from Christ in this form to lead to starvation and spiritual death.
One day St Anthony was challenged by a heretic who didn’t believe in the true presence of Jesus in the Eucharist. He taunted the illustrious Saint saying he’d believe only if his mule bowed down to it.
They fixed a day for this test: the next three days. The heretic went ahead and starved the mule all the while hoping to tilt nature to his favour. When the time came, St Anthony stood at a corner with the Eucharist in his hands while the heretic stood to the other side with some fodder for the hungry mule to be attracted to it and feed. The mule, ignoring the 3-day-old hunger went before the Eucharist, knelt and adored Jesus.
When the heretic saw this he immediately knelt down and professed his faith in the real presence of Jesus in the Eucharist.
The Lord is really in the Eucharistic Species
“That in this sacrament are the true Body of Christ and his true Blood is something that ‘cannot be apprehended by the senses,’ says St. Thomas, ‘but only by faith, which relies on divine authority.’ For this reason, in a commentary on Luke 22:19 (‘This is my body which is given for you.’), St. Cyril says: ‘Do not doubt whether this is true, but rather receive the words of the Savior in faith, for since he is the truth, he cannot lie.'”
Godhead here in hiding, whom I do adore
Masked by these bare shadows, shape and nothing more,
See, Lord, at thy service low lies here a heart
Lost, all lost in wonder at the God thou art.
Seeing, touching, tasting are in thee deceived;
How says trusty hearing? that shall be believed;
What God’s Son has told me, take for truth I do;
Truth himself speaks truly or there’s nothing true. – CCC 1381