Final answer:
The shepherds were to find the baby Jesus wrapped in cloths and lying in a manger, which was a sign of his humble birth. Art often depicts Jesus as the Good Shepherd, furthering the association of shepherds with early Christian theology.
Step-by-step explanation:
The sign the shepherds were to look for when searching for Jesus was a unique one, as recounted in the Bible, specifically in the Gospel of Luke. They were told by an angel that they would find the baby Jesus wrapped in cloths and lying in a manger. This was considered the sign because it was highly unusual for a newborn king, the awaited Messiah, to be found in such humble circumstances. The manger signified the humble birth of Jesus, contrasting with the expectations of a royal birth in grandeur, thus making it a clear marker for the shepherds.
Imagery throughout early Christian art, like the mosaics found in Italy, often depicted Jesus as the Good Shepherd caring for his flock. This representation links back to the biblical narrative and connects the significance of shepherds in Christian theology. In the story of Jesus's birth, the shepherds were among the first to receive the announcement of the new Savior, emphasizing their importance in the Christian faith tradition.