It has been observed that, on the occurrence of great events, and of mighty changes in terrestrial things, such stars are wont to appear, indicating either the removal of dynasties or the breaking out of wars, or the happening of such circumstances as may cause commotions upon the earth. But we have read in the Treatise on Comets by Chæremon the Stoic, that on some occasions also, when good was to happen, comets made their appearance; and he gives an account of such instances.
If, then, at the commencement of new dynasties, or on the occasion of other important events, there arises a comet so called, or any similar celestial body, why should it be matter of wonder that at the birth of Him who was to introduce a new doctrine to the human race, and to make known His teaching not only to Jews, but also to Greeks, and to many of the barbarous nations besides, a star should have arisen? Now I would say, that with respect to comets there is no prophecy in circulation to the effect that such and such a comet was to arise in connection with a particular kingdom or a particular time; but with respect to the appearance of a star at the birth of Jesus there is a prophecy of Balaam recorded by Moses to this effect: “There shall arise a star out of Jacob, and a man shall rise up out of Israel.” And now, if it shall be deemed necessary to examine the narrative about the Magi, and the appearance of the star at the birth of Jesus, the following is what we have to say, partly in answer to the Greeks, and partly to the Jews.
Source: Against Celsus (New Advent)