An angel appeared to him in a dream and told him to.
Saying, Arise, and take the young child and his mother, and go into the land of Israel: for they are dead which sought the young child's life. Matthew 2:19-20
When Herod was dead, behold, an angel of the Lord appeareth in a dream to Joseph in Egypt, Saying, Arise, and take the young child and his mother, and go into the land of Israel: for they are dead which sought the young child's life. Matthew 2:19-20
http://www.thebricktestament.com/the_gospels/jesus_is_born_02/mt02_19-20.jpg
