And again the name, ‘Mary’ befits her, which is (also) interpreted as ‘Star of the Sea,’ for as by this star seafarers are directed to port, so are Christians guided to glory by Mary.
Saint Thomas Aquinas
There are three things contained in this (angelic) salutation. The first part comes from the Angel, Gabriel, namely, “Hail, full of grace, the Lord is with you; blessed are you among women.” The second part comes from Elizabeth, the mother of John the Baptist, namely, “Blessed is the fruit of thy womb.” The Church adds the third part, to wit, “Mary,” for the Angel did not say, “Hail, Mary,” but rather, “Hail, full of grace.” Still, this name ‘Mary,’ according to its meaning, befits the Angel’s words, as we shall see.
“Hail Mary, full of grace, the Lord is with thee”
With respect to the first part, consider that in ancient times it was exceedingly great for an Angel to appear to men, or, that men might offer them reverence was held to be a great honor. Hence, to the honor of Abraham it is written that he received angelic guests and showed them reverence. That an Angel reverence a man, however, was never heard of until the Angel reverently greeted the Blessed Virgin, saying, “Hail.”
That in ancient times the Angel did not reverence man, but rather man reverenced the Angel comes from the fact that the Angel is greater, and greater with respect to three things. First, with respect to dignity, since the Angel is a spiritual nature: “You make your Angels to be spirits, etc.” (Ps. 103,4). Man, indeed, is corruptible by nature, for which reason Abraham said: “I am speaking to the Lord, I, who am but dust and ashes” (Gen 18,27). Second, with respect to their familiarity with GOD, for the Angel belongs to the household of GOD (‘familiaris’) inasmuch as he assists Him. “A thousand times a thousand minister to Him, and ten thousand myriads assist Him.” (Dan 7,10). Man, though, is like a stranger, set off from GOD by sin: “I withdrew in flight” (Ps 54,8). Therefore, it was fitting that man should reverence the Angel as one on close and familiar terms with the king (‘propinquum and familiarem regis’!). Third, the Angel took preeminence on account of the plenitude of the splendor of divine grace. The Angels, namely, participate in the light of divine grace itself in the very highest degree. “Is there any number to His armies upon whom His light does not arise?” (Job 25,3). And this is why they always appear with light. But men, even though they participate somewhat in the light of grace, do so only slightly and in obscurity.
Consequently, it was unfitting that men be shown reverence until someone should be found in this (human) nature who exceeds the angels in these three points. And this was the Blessed Virgin. In order to indicate that she exceeded them in these three points the Angel wished to offer her reverence, saying “Hail.”