Elohim
That the Hebrew plural is often used for a singular noun to denote “a ‘plural’ of majesty or excellence” is well-known by all Biblical Hebrew language experts and has been known from at least the time of Gesenius (1786-1842), who is still regarded as one of the best authorities for Biblical Hebrew!
Gesenius’ Hebrew-Chaldee Lexicon to the Old Testament (“long regarded as a standard work for students”), p. 49, shows that elohim (“God/gods”) is sometimes used in a numerically plural sense for angels, judges, and false gods. But it also says,
“The plural of majesty [for elohim], occurs, on the other hand, more than two thousand times.” And that elohim when used in that sense “occurs in a [numerically] singular sense” and is “constr[ucted] with a verb ... and adjective in the singular.”
Gesenius - Kautzsch’s Hebrew Grammar, 1949 ed., pp. 398, 399, says:
“The pluralis excellentiae or maiestatis ... is properly a variety of the abstract plural, since it sums up the several characteristics belonging to the idea, besides possessing the secondary sense of an intensification of the original idea. It is thus closely related to the plurals of amplification .... So, especially Elohim ... ‘God’ (to be distinguished from the plural ‘gods’, Ex. 12:12, etc.) .... That the language has entirely rejected the idea of numerical plurality in Elohim (whenever it denotes one God) is proved especially by its being almost invariably joined with a singular attribute.”
Peloubet’s Bible Dictionary, 1925 ed. Pg. 224:
Elohim "is either what grammarians call the plural of majesty, or it denotes the fullness of divine strength, the sum of the powers displayed by God."
More modern publications (trinitarian Protestant and Catholic) also make similar acknowledgments of the intended plural of majesty or excellence meaning for elohim. (See the New Catholic Encyclopedia, 1967, Vol. v., p. 287.)
Nelson’s Expository Dictionary of the Old Testament, describes elohim:
“The common plural form ‘elohim,’ a plural of majesty.” - Unger and White, 1980, p. 159.
“Pluralis Majestatis: Biblical Hebrew
"The term ‘majestic plural’ or pluralis majestatis refers to the use of a plural word to refer honorifically to a single person or entity. It is also called the ‘plural of respect’, the ‘honorific plural’, the ‘plural of excellence’, or the ‘plural of intensity’. In the Hebrew Bible such plural forms are most commonly used when referring to the God of Israel, e.g., adonim ‘I am a master (lit. ‘masters’)’ (Mal. 1.6), although it can also be used when referring to a human, e.g., abraham adonaw ‘Abraham his master (lit. ‘masters’)’ (Gen. 24.9), an object, e.g. gibroteka ‘your grave (lit. ‘graves’)’ (2 Kgs 22.20), ...." - Encyclopedia of Hebrew Language and Linguistics, p. 145, vol. 3, 2013.
The International Standard Bible Encyclopedia says:
“It is characteristic of Heb[rew] that extension, magnitude, and dignity, as well as actual multiplicity, are expressed by the pl[ural].” - Eerdmans Publishing Co., 1984 ed., Vol. II, p. 1265.
Today’s Dictionary of the Bible, 1982, Bethany House Publishers, written by trinitarian scholars, says of elohim:
“Applied to the one true God, it is the result in the Hebrew idiom of a plural magnitude or majesty. When applied to the heathen gods, angels, or judges ..., Elohim is plural in sense as well as form.” - p. 208.
The famous trinitarian scholar, Robert Young, (Young’s Analytical Concordance and Young’s Literal Translation of the Bible) wrote in his Young’s Concise Critical Commentary, p. 1,
“Heb. elohim, a plural noun ... it seems to point out a superabundance of qualities in the Divine Being rather than a plurality of persons .... It is found almost invariably accompanied by a verb in the singular number.”
Exodus 7:1 (KJV and Hebrew text) shows God calling Moses "a god" (elohim). This alone shows the error of some that the plural elohim must mean a "plural oneness" unless we want to believe Moses was a multiple-person Moses!
And The New International Dictionary of New Testament Theology, Zondervan Publishing, 1986, tells us:
“Elohim, though plural in form, is seldom used in the OT as such (i.e. ‘gods’). Even a single heathen god can be designated with the plural elohim (e.g. Jdg. 11:24; 1 Ki. 11:5; 2 Ki. 1:2). In Israel the plural is understood as the plural of fullness; God is the God who really, and in the fullest sense of the word, is God.” - p. 67, Vol. 2.
The NIV Study Bible says about elohim in its footnote for Gen. 1:1:
“This use of the plural expresses intensification rather than number and has been called the plural of majesty, or of potentiality.” – p. 6, Zondervan Publ., 1985.
And the New American Bible (St. Joseph ed.) tells us in its “Bible Dictionary” in the appendix:
“ELOHIM. Ordinary Hebrew word for God. It is the plural of majesty.” – Catholic Book Publishing Co., 1970.
A Dictionary of the Bible by William Smith (Smith’s Bible Dictionary, p. 220, Hendrickson Publ.) declares:
“The fanciful idea that [elohim] referred to the trinity of persons in the Godhead hardly finds now a supporter among [real] scholars. It is either what grammarians call the plural of majesty, or it denotes the fullness of divine strength, the sum of the powers displayed by God.”
And the prestigious work edited by Hastings says about this:
"It is exegesis of a mischievous if pious sort that would find the doctrine of the Trinity in the plural form elohim [God]" ("God," Encyclopedia of Religion and Ethics).