4 But the wise men perceive nothing of this, by reason of their exceeding reverence (for they never could have expected that he could have gone on to so great wickedness, and would have attempted to form plots against a dispensation so marvellous): and they depart suspecting none of these things, but from what was in themselves auguring all that would be in the rest of mankind.
“And, lo! The star, which they saw in the east, went before them.”
For therefore only was it hidden, that having lost their guide, they might come to be obliged to make inquiry of the Jews, and so the matter might be made evident to all. Since after they have made inquiries, and have had His enemies for informants, it appears to them again. And mark how excellent was the order; how in the first place after the star the people of the Jews receives them, and the king, and these bring in the prophecy to explain what had appeared: how next, after the prophet, an angel again took them up and taught them all things; but for a time they journey from Jerusalem to Bethlehem by the guidance of the star, the star again journeying with them from that place also; that hence too you might learn, that this was not one of the ordinary stars, for there is not so much as one star that has this nature. And it not merely moved, but “went before them,” drawing and guiding them on in mid-day.
“But what need of this star any more,” one may ask, “when the place was ascertained?” In order that the Child also might be seen. For there was not anything to make Him manifest, since the house was not conspicuous, neither was His mother glorious, or distinguished. There was need then of the star, to set them by the place. Wherefore it re-appears on their coming out of Jerusalem, and stays not, before it has reached the manger.
And marvel was linked on to marvel; for both were strange things, as well the magi worshipping, as the star going before them; and enough to attract even such as were made all of stone. For if the wise men had said, they had heard prophets say these things, or that angels had discoursed with them in private, they might have been disbelieved; but now, when the vision of the star appeared on high, even they that were exceeding shameless had their mouths stopped.
Moreover, the star, when it stood over the young Child, stayed its course again: which thing itself also was of a greater power than belongs to a star, now to hide itself, now to appear, and having appeared to stand still. Hence they too received an increase of faith. For this cause they rejoiced also, that they had found what they were seeking, that they had proved messengers of truth, that not without fruit had they come so great a journey; so great a longing (so to speak) had they for Christ. For first it came and stood over His very head, showing that what is born is Divine; next standing there, it leads them to worship Him; being not simply barbarians, but the wiser sort among them.
Do you see, with how great fitness the star appeared? Why; because even after the prophecy, and after the interpretation of the chief priests and scribes, they still had their minds turned towards it.
Source: Homilies on the Gospel of St. Matthew (New Advent)