While he was thinking about these things, now, an angel of the Lord appeared to him in a dream and said, “Joseph, son of David, do not be afraid to take Mary as your wife, for what has been conceived in her is from the Holy Spirit.”
This word shows how God directs Joseph’s mind by revealing the profound meaning of His plan of salvation. Joseph, being a righteous and prudent man, desired to act according to God’s will, but he did not know that Mary’s pregnancy was not the result of sin, but of divine providence. In that moment of reflection, the angel of the Lord appeared to Joseph, explaining that Mary’s pregnancy is from the Holy Spirit. The title “son of David” reminds Joseph of his genealogical calling and the messianic promise: he was to become Christ’s earthly guardian, receiving into his home the Child who is the Son of God.