The phrase Κύριός μου (= My Lord) occurs in the NT quite sparingly, just 11 times, and always refers to Jesus as a formal but still personal form of address. Jesus is often referred to as, "the Lord", as indeed are others such as Caesar, etc; but only Jesus is ever referred to as "my Lord"; for example -
Speaking directly to Jesus or about Jesus: Luke 1:43 (Elizabeth), John 20:13 (Mary), 28 (Thomas), Phil 3:8 (Paul), Matt 22:44, Mark 12:36, Luke 20:42, Acts 2:34 plus some parables as well.
These all appear to be quoting just two OT sources namely
- Ps 110:1 - clearly a Messianic Psalm as quoted in Matt 22:44, Mark 12:36, Luke 20:42, Acts 2:34
- Ps 35:23 as per the LXX were we find the phrase, ὁ θεός μου καὶ ὁ κύριός μου = the God of me and the Lord of me. Thomas (John 20:28) particularly appears to almost quote this verbatim!
In Luke 1:43 we have a similar instance about which Ellicott observes:
(43) Whence is this to me . . .?—The sudden inspiration bids
Elizabeth, rising above all lower thoughts, to recognise that the
child of Mary would be also the Son of the Highest. The contrast
leaves no room for doubt that she used the word “Lord” in its highest
sense. “Great “as her own son was to be (Luke 1:15) in the sight of
the Lord, here was the mother of One yet greater, even of the Lord
Himself.
Matthew Poole arrives at a similar conclusion:
Elisabeth in these words acknowledgeth both the incarnation of Christ,
and the union of the Divine and human nature in the one person of the
Mediator; she acknowledgeth Christ her Lord, and Mary to be his
mother.
Hence, by divine inspiration of the Holy Spirit, Elizabeth uttered a sublime truth that was a simple fact - Mary was the human mother of the Lord of the all the earth, whom she correctly addressed as "My Lord". The Pulpit commentary also observes:
And whence is this to me, that the mother of my Lord
should come to me? But the Holy Ghost (verse 41) raised Elisabeth's
thoughts yet higher. Not only did she bless the mother of the coming
Messiah, but the Spirit opened her eyes to see who that coming Messiah
really was. Very vague indeed was the conception of the coming Messiah
in Israel. The truth was, perhaps, revealed, and in rapt moments
received by men like Isaiah and Ezekiel; and now and again men like
David; Daniel wrote down visions and revelations respecting the Coming
One, the true purport of which vision they scarcely grasped. Generally
the Messianic idea among the people pictured a hero greater than Saul,
a conqueror more successful than David, a sovereign more magnificent
than Solomon. ... But here the Spirit in a moment revealed to the
happy wife of the priest Zacharias that the Babe to be born of her
young kinswoman was not only the promised Messiah, but was the awful
Son of the Highest!