Late 3rd or early 4th century
Detail of the so-called "Sarcophagus of Stilicho"
Basilica of St. Ambrose, Milan
This "sarchophagus" has been in use for a thousand years as the base for the pulpit at the basilica. Cartlidge and Elliott (18) date this part of it to the late 3rd or early 4th century.
Modern eyes are accustomed to Nativity images with Mary, Joseph, and perhaps some shepherds and angels, but in this early work the ox and ass were more important because they form a declaration that this child's birth was a fulfillment of prophecy. In Isaiah 1:3 "The ox knoweth his owner, and the ass his master's crib: but Israel hath not known me, and my people hath not understood." This was taken to be a prophecy of the birth of Christ, when the child was "laid in a manger" (Luke 2:7). (The words translated into English "crib" and "manger" are both praesepe in the Latin Vulgate and φάτνην in the Greek texts used by early Christians.)
The Nativity also has relevance to the Eucharist in that, as the commentators put it, the ox and ass at their feeding trough represent the Christian faithful who are nourished by the "fodder" of Christ's flesh.1 This point is emphasized by the birds pecking at baskets of bread at the left and right ends of the tympanum. In both Christian and pagan art of the time birds were a common symbol of the soul.2 Bread is of course used in the Eucharistic rite, and the baskets are very similar to those seen in this period in images of the multiplication of the loaves (example). Christ himself explains the spiritual meaning of those loaves in John 6:35, "I am the bread of life: he that cometh to me shall not hunger: and he that believeth in me shall never thirst."
The border of swastikas and rosettes encircles the entire sarcophagus, separating the large narrative panels below from the tympanum shapes above. In ancient times swastikas and rosettes were common symbols of the sun. Other religions sometimes associated them with specific gods, but here their purpose seems to be purely decorative.
Read more about images of the birth of Jesus.
Source: this page at Wikimedia Commons..