The stories of Jesus' birth are stories of travel. In the Gospel of Luke, Mary and Joseph travel through the national territory, from Nazareth in Jewish Galilee to Bethlehem in Jewish Judea.
In Matthew's Gospel, the travel is international. The tale begins with the wise men traveling from the "East." They visit King Herod to ask for directions and then bring gifts to Mary, Joseph and Jesus in Bethlehem. After they leave, an angel sends Joseph and his family to Egypt, where they live until Herod's death.
So with all this international travel, how did the travelers communicate? What languages did they speak at home and abroad? Our answer to this question lies in understanding the languages spoken in Palestine and the extent to which they would have been used in the East and in Egypt.
Linguistically, Palestine was a cosmopolitan region in the first centuries B.C. and A.D. As a strip of land less than 75 miles wide on the eastern Mediterranean shore, Palestine often found itself between empires or swallowed up by one. Whether it was Egypt or Mesopotamia, or Persia, Greece or Rome, these imperial powers moved across Palestine, warred on its territory, and often absorbed Palestine into their territories.
So although Hebrew was the Jews' native language, by the time of Jesus' birth, they had centuries of experience with both Aramaic and Greek. Babylonia and Persia had brought them Aramaic as early as the eighth century B.C. When Alexander the Great conquered Palestine in 332 B.C., Greek became the imperial language. When the Romans arrived in 63 B.C., Greek retained its dominant role.
Both Persia and Alexander conquered wide swaths of territory beyond Palestine, ranging from Egypt to modern day Iraq and Iran far to the east. So all the conversations in the nativity story should have happened in Greek, right? Greek was the most recent language, it was used in Palestine, Egypt and the "East," and had been around for several centuries. Seems obvious.
If only it were so simple.
In the highly stratified societies of the ancient world, language did not change at the same speed at all social levels. The elite and educated classes learned a new imperial language most quickly, because the conquerors, who were relatively few in number, used them to rule the conquered country. The next group to pick up a new language was the traders and other business people, while the last was the peasants. Their fixed tie to their farms usually required interaction with the rulers only at tax-collecting time, and then probably through their own countrymen.
This was the main pattern of language acquisition for both Aramaic and Greek in this region. But after Alexander, a new linguistic development took place. As the elites learned Greek, Aramaic became the language of resistance. Among the lower classes, Aramaic was already in the process of replacing their native languages and this process continued until it was the lingua franca not just of Palestine but of all the eastern Mediterranean countries.
Apparently the upper classes retained Aramaic as well, for the inscriptions and documents of private individuals or local communities unearthed by archaeologists in this region are in Aramaic more frequently than in Greek. The elite may have spoken Greek to their conquerors, but they spoke Aramaic at home.
So when the upper-class "wise men" talked with King Herod, presumably in his Jerusalem palace, they probably conversed in the official language of Greek.
But when they arrived in Bethlehem, they most likely spoke the same language that Joseph and Mary were using with the local villagers, namely, Aramaic. As a carpenter, Joseph belonged to the artisan classes rather than the peasants, but the nationalist character that Aramaic had taken on would have made this his primary language.
So what language did Joseph and Mary speak in Egypt? Probably Aramaic. For the same phenomenon of linguistic resistance among the lower classes took place in Egypt as well as Palestine. Joseph and his family would have lived among the lower classes while they were in Egypt, and so would not have had any connection to the elite circles where Greek would have been the language of conversation.
This fits with the gospel's portrayal of the adult Jesus. Although the gospels are written in Greek, the shared language of the eastern Mediterranean, when they depict Jesus speaking in his native language-as in his final words on the cross-he speaks Aramaic.