At a medieval church festival, the priest brayed like a donkey and the congregation brayed back

The Feast of the Ass was a medieval Christian celebration held on January 14, honoring the donkey that carried the Holy Family into Egypt. A girl and a child riding a real donkey would be led through town to the church, where the animal stood beside the altar during the sermon.

A 13th-century manuscript from Beauvais describes the full service. The congregation sang nine stanzas of Latin praise to the donkey, each ending with a French refrain: "Hez, Sire Asnes, car chantez, / Belle bouche rechignez" — "Up! Sir Ass, and sing. Open your pretty mouth." The rubric then specifies: "At the end of Mass, the priest turned to the spectators. In lieu of saying the 'Ite missa est', will bray thrice; the people, instead of replying 'Deo Gratias', say 'Hinham, hinham, hinham.'"

The festival grew out of the Processus Prophetarum, a dramatic dialogue in which Old Testament prophets testified to the coming of the Messiah. Balaam's talking donkey stole the show every time, and the whole ceremony gradually became known as the crowd's favorite. The feast disappeared in the second half of the 15th century, stamped out along with the related Feast of Fools.