Cristóbal de Morales no relation Christmas
History
The image of the oxen and donkey next to the crib is found in Isaiah (Isa. 1.3) and is traditionally related to the nativity scene at the birth of Jesus in Luke 2. Luke (Lk 2.7) does not mention animals, but a manger. In the apocryphal Gospel of Pseudo-Matthew, both animals are specifically named. The image continued to spread from the 13th century onwards when it was included in the Golden Legend. It became the most popular symbol for the mystery of the self-abasement of God in his Incarnation. (Phil 2,6–7).
The second part of the responsory is a versicle – a short prayer to Mary, mother of Jesus – which is based on the words with which Elizabeth welcomes Mary on her visitation (Lk 1.42–43). Most polyphonic settings of the text omit the versicle. The setting by Cristóbal de Morales includes a different versicle. 
David Thompson states that "the origin of this Nativity poem is in itself a great mystery. It is not a biblical text. The poem/chant was incorporated in mediaeval times into the Divine Office as the fourth of the nine Responsories for Matins on Christmas Day." He conjecturally dates its incorporation to the liturgical reforms of Pope Gregory VII.
no relation