But while he thought on these things, behold, the angel of the Lord appeared unto him in a dream, saying, Joseph, son of David, fear not to take unto you Mary your wife: for that which is conceived in her is of the Holy Spirit.
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Ambrose of Milan
In this word “appeared” is conveyed the power of Him that did appear, allowing Himself to be seen where and how He pleases.
Be not troubled that he calls her his wife; for she is no therein robbed of her virginity, but her wedlock is witnessed to, and the celebration of her marriage is declared.