“When he arose, he took the young child and his mother by night, and departed into Egypt:”
And he rose and took the child and his mother by night and departed to Egypt. Joseph's immediate nighttime departure — no delay, no discussion, no waiting for daylight — is the same quality of obedience he showed in verse 24 of chapter 1. The pattern is consistent: Joseph receives the divine word and acts. The Gospels record almost no words spoken by Joseph; his entire contribution to the story is in actions. He is the silent righteous man who carries out what he is told and thereby protects both the child and the covenant. Hebrews 11:8 describes Abraham obeying when he was called to go, even though he did not know where he was going — Joseph's nighttime flight to Egypt carries the same quality of prompt obedience to a specific but open-ended command.
Church Fathers on Matthew 2:14
Here Matthew omits the day of purification when the first-born must be presented in the Temple with the lamb, or a pair of turtle doves, or pigeons. Their fear of Herod did not make them bold to transgress the Law, that they should not present the Child in the temple. As soon then as the rumour concerning the Child begins to be spread abroad, the Angel is sent to bid Joseph carry Him into Egypt.
by this that the Angel appears always to Joseph in sleep, is mystically signified that they who rest from mundane cares and secular pursuits, deserve angelic visitations.
The first time when he would teach Joseph that she was lawfully espoused, the Angel called the Virgin his espoused 'wife;' but after the birth she is only spoken of as the Mother of Jesus. As wedlock was rightfully imputed to her in her virginity, so virginity is esteemed venerable in her as the mother of Jesus.