The Magi

Now after Jesus was born in Bethlehem of Judea in the days of Herod the king, behold, wise men from the east came to Jerusalem, 2 saying, “Where is he who has been born king of the Jews? For we saw his star when it rose and have come to worship him"…12 And being warned in a dream not to return to Herod, they departed to their own country by another way (Mt 2:1-2,12).

Commentators are puzzled by how the Magi connected the star to the birth of Jesus. That the Magi might connect a striking stellar phenomenon to the birth of a significant personage is not surprising. In the ancient world, astronomical "prodigies" were often thought to portend significant events, like a royal birth. 

What's puzzling is the specificity of the association. How does the star single out the birth of Jesus? 

According to one theory, the Magi came from Babylonia. There was a Jewish community in Babylonia. Due to the duration of the Babylonian Exile, you had second and third-generation Jews who were born there. Some of them stayed behind because, for them, that was home. They didn't view themselves as expatriates. For them, Palestine was a foreign land. So it's possible that the Magi learned about Num 24:17 from their Jewish neighbors. 

That's all very iffy, but it's one possible explanation. However, v12 might suggest another possible source of information. Since these particular Magi were subject to revelatory dreams, that might supplement their astrological observations. They don't mention this to Herod, but there's no reason to expect they'd give him a full debriefing of all the factors that led them to Jerusalem.