The punctuation does not exist in the original text, but is supplied by translators. Since lots of translators assume Joseph didn’t believe Mary was pregnant by the Holy Spirit, they add a semi-colon to the angel’s message to Joseph. However, Jerome, the greatest scripture scholar of antiquity, thought that Joseph believed Mary (I think so too) and wanted to put her away, not because he thought her an adulteress, but because he was frightened to assume paternity of the awesome and terrifying child in her womb. Given that, dropping a single semi-colon completely changes the meaning of the angel’s message to Joseph:
Note that the angel in the dream does not say to Joseph, “Don’t suspect Mary of adultery, of being unfaithful to her promise to marry you.” Rather, the angel says, “Do not fear to take Mary your wife.” Instead of reading, “Do not fear to take Mary your wife <stop> for that which is conceived in her is of the Holy Spirit,” let’s try dropping the semicolon. If we do that, we get, “Do not fear to take Mary your wife because that which is conceived in her is of the Holy Spirit.” That is, “Do not be afraid to take Mary your wife into your home ON ACCOUNT OF THE FACT THAT the child she is carrying is of the Holy Spirit.” That changes the meaning entirely, doesn’t it!
Fascinating. His whole homily is here.