Adonai and adoni (Psalm 110:1: "The LORD says to my lord...")
The Bible’s supreme proof text for telling the difference between the One God and the Messiah who is not God
This verse was referred to the Messiah by the Pharisees and by Jesus. It tells us that the relationship between God and Jesus is that of Deity and non-Deity. The Messiah is called adoni (my lord), and in every one of its 195 occurrences adoni (my lord) means a superior who is not God. The word Adonai on the other hand refers exclusively to the one God in all of its 449 occurrences. Adonai is the title of Deity and adoni never designates Deity.
If the Messiah were called Adonai this would introduce two Gods into the Bible and would be polytheism. Psalm 110:1 should guard us all against supposing that there are two who are God. In fact the Messiah is the supreme human being and agent of the one God. Psalm 110:1 is the Bible’s master text for defining the Son of God in relation to the one God, his Father.
Why is it that a number of commentaries misstate the facts about Psalm 110:1? They assert that the word for the Messiah in Psalm 110:1 is Adonai. It is not. These commentaries seem to obscure a classic text defining God in relation to His Son. The Hebrew text assigns to the Messiah the title adoni which invariably distinguishes the one addressed from the Deity. The Messiah is the supreme human lord. He is not the Lord God (cp. 1 Tim. 2:5; 1 Cor. 8:4-6; Mark 12:28-32).
The Word Biblical Commentary is right: "The first [word] is the tetragrammaton (the personal name 'Yahweh,' which was not spoken by the Jews, who substituted the word adonay [or adonai], i.e. a word virtually identical to the second word); the second is adoni, 'my lord.' David calls his son not Yahweh but adoni, 'my lord': 'Yahweh [the Lord] said to my lord'" (Matthew, Word Biblical Commentary, p. 651).
Why is the Messiah called adoni (my lord) and never Adonai (Lord God)?
“Adonai and adoni are variations of Massoretic pointing to distinguish divine reference from human.”
(Brown, Driver and Briggs, Hebrew and English Lexicon of the Old Testament, under adon).“The form adoni (‘my lord’), a royal title (1 Sam. 29:8), is to be carefully distinguished from the divine title Adonai ('my Lord,' 'Lord,' or 'O Lord'), used over 130 times of Yahweh.”
(“Lord,” International Standard Bible Encyclopedia, Vol. 3, p. 157).“Lord. This term in the OT is used to translate ADONAI when applied to the Divine Being. The [Hebrew] word…is with suffix with [special pointing], presumably for the sake of distinction…between a divine or a human appellative.”
("Lord,” Hastings Dictionary of the Bible, Vol. 3, p. 137).“Hebrew Adonai exclusively denotes the God of Israel. It is attested about 450 times in the OT…Adoni [is] addressed to human beings (Gen. 44:7, Num. 32:25, 2 Kings 2:19 [etc.]). We have to assume that the word Adonai received its special form to distinguish it from the secular use of adon [i.e., adoni]...The reason why this is written Adonai instead of the normal adon, adoni...may have been to distinguish Yahweh from other gods and from human lords.”
("Lord," Dictionary of Deities and Demons in the Bible, p. 531-532).“The extension [lengthening] of the a [on Adonai, the Lord God] may be traced to the concern of the Massoretes to mark the word as sacred by a small outward sign.”
(Theological Dictionary of the NT, Vol. 3, p. 1060-1061).“None of the forms of ‘my lord’ (adoni) is a divine reference...These observations lend further credence to the generally accepted fact that the masoretic pointing distinguishes divine references (Adonai) from human references (adoni).”
(Herbert Bateman, “Psalm 110:1 and the New Testament,” Bibliothecra Sacra 149, 1992, p. 448).“F. Brown, S.R. Driver, and C.A. Briggs observe further that variations of pointing, particularly between adoni and adonay, are set forth to distinguish between human and divine referents, respectively. In our analysis of all 774 occurrences of the adon root in the Hebrew Bible, we have found this to be strikingly true in the case of these two forms: adoni (see Ps. 110:1) almost always refers to a human lord/master (in a handful of occurrences, the referent is an angelic figure), while adonay (see Ps. 110:5) always refers to the divine Lord.”
(Murray Smith, Ian Vaillancourt, “Enthroned and Coming to Reign: Jesus’s Eschatological Use of Psalm 110:1 in Mark 14:62,” Journal of Biblical Literature, Vol. 141:3, 2022, p. 516-517).