It is said to be the gray donkey, which carried the Blessed Virgin on its back to the barn.
Just as essential as the ox in the crib, the donkey is the most widespread animal in the peasant world. We find him in the manger lying to the right of Jesus, his head bent towards the Child Jesus.
According to the Fathers of the Church — Origen, Ambrose — and following Isaiah, the donkey represents the Gentiles bending under the weight of idols, and the ox the Jews, for, like the latter, it bears the yoke of law.
The Franciscan tradition insists on the extreme poverty of Joseph and Mary, on the birth of Jesus in cold and hardship. In the apocryphal gospels (Gospel of Pseudo-Matthew) the animals warm the newborn child with their breath.