Jamieson, Fausset and Brown on Matthew 2:13

13. And when they were departed, behold, the angel of the Lord appeareth to Joseph in a dream, saying, Arise, and take the young child and his mother--Observe this form of expression, repeated in Mt 2:14--another indirect hint that Joseph was no more than the Child's guardian. Indeed, personally considered, Joseph has no spiritual significance, and very little place at all, in the Gospel history.

and flee into Egypt--which, being near, as Alford says, and a Roman province independent of Herod, and much inhabited by Jews, was an easy and convenient refuge. Ah! blessed Saviour, on what a checkered career hast Thou entered here below! At Thy birth there was no room for Thee in the inn; and now all Judea is too hot for Thee. How soon has the sword begun to pierce through the Virgin's soul (Lu 2:35)! How early does she taste the reception which this mysterious Child of hers is to meet with in the world! And whither is He sent? To "the house of bondage?" Well, it once was that. But Egypt was a house of refuge before it was a house of bondage, and now it has but returned to its first use.

and be thou there until I bring thee word; for Herod will seek the young child to destroy him--Herod's murderous purpose was formed before the Magi had reached Bethlehem.