One God, three persons.
What should end the dispute is that it is used in the plural as well in Deut 6:4 where there it is plainly referring to the singular God.
Here is an analysis of the tense by Wheeler. (I had to get rid of the Hebrew formatting so it is missing some of the examples.)
HEBREW NOUNB.\tThe Plural in Hebrew Nouns:
1.\tThe Forms of Plural Hebrew Nouns: The Plural form in Hebrew is created chiefly by the addition of suffixes to the Singular Noun Form:
a.\tMasculine Plural:
i)\tThe standard Masculine Plural termination is:
a)\tThe standard Masc. Pl. termination sometimes occurs on apparently Feminine nouns:
ii)\tAramaic Termination: Occassionally Nouns take the same ending as Aramaic plurals: Prov 31:3
iii)\tFeminine Termination: The normal feminine plural termination - also occurs on masculine nouns: Jer 7:18
iv)\tFeminine + Masculine Termination: Sometimes both feminine and masculine plural terminations occur on the same noun, when the noun is construct: Num 32:8
b.\tFeminine Plural:
i)\tThe standard Feminine Plural termination is:
a)\tThe standard Fem. Pl. termination occurs on masculine nouns as well; see above
ii)\tMasculine Termination: Some feminine nouns take the standard masc. pl. termination: 1 Sam 25:18
iii)\tFeminine + Masculine Termination: Sometimes both feminine and masculine plural terminations occur on the same noun, when the noun is construct: Isa 14:14
Uses of the Plural with Hebrew Nouns:
a.\tTo indicate simple plurality: kings, altars.
b.\tTo indicate composition: pieces of silver (Gen 42:25), firewood (Gen 22:3), clods of earth (Prov 8:26).
c.\tTo indicate natural products in an unnatural or manufactured condition: 'wheat,' in grains (threshed wheat) as distinguished from 'wheat,' in the ear; 'barley,' in grains versus 'barley,' in the ear. References: GKC §124 m calls this the plural of result.
d.\tTo indicate extension: This "extension" use of the plural is also used for
i)\t[b]Multiple Parts considered as a Whole: The object consists of separate parts or points: 'posterior parts,' 'back,' 'face,' 'neck.'[/b]
ii)\tAreas of space: 'heaven,' 'water,' 'region on the other side,' or
iii)\tPeriods of time: 'life,' 'lifetime,' 'eternity.' (everlasting ages) 'time of youth,' 'youth,' 'time of old age,' 'old age.'
iv)\tPlural of 'blood':a)\tThe Singular: Used when the blood is regarded as an organic unity: e.g., menstrual blood, blood of sacrifices (collected in a basin).b)\tThe Plural: Indicates blood in the state of dispersion: e.g., spots or pools of blood, blood stains.c)\tBy the figure of metonymy the plural 'blood' in dispersion is used: References: Bullinger, Figures of Speech Used in the Bible, p. 585 ff.:(1)\tof 'bloodshed.' (Hos 1:4) i.e. murder,(2)\tof 'bloodguiltiness' (Ex 22:1 ).
e.\tTo indicate abstract ideas: The abstract plural may express the idea of a combination of conditions, qualities, or characteristics inherent in the idea of the stem, or sum up the various single acts of which an action is composed. References: GKC §124 d -f distinguish the following abstract plurals:
i)\tAbstract plural of quality (JMG §136 g): (originally) 'secure things,' or 'secure circumstances' then > 'safety,' 'faithfulness,' 'integrity.'
ii)\tAbstract plural of state: state of 'virginity,' state of 'blindness,'
iii)\tAbstract plural of actions which sums up the several parts of an action (GKC §124 ): 'ordination' to the priesthood (properly 'filling' of the hand), 'atonement.'
iv)\tAbstract plural of intensification in which the idea of the stem is intensified (GKC §124 e ): (true) 'counsel' (Deut 32:28); (thorough, complete) 'knowledge' (Isa 2:3).
f.\tTo indicate respect: This use of the plural has also been called the plural of eminence (DHS §16 c) or the plural of excellence or majesty (GKC §124 g ).
i)\tGKC §124 g explains that this usage is probably an extension of the abstract plural of quality or the abstract plural of intensification in which the several characteristics of the idea of the stem are summed up or intensified.
ii)\t[b]Examples are (the true)'God, 'the most holy,' (the true) 'Lord.'[/b]
iii)\tAttributive adjectives are regularly formed in the singular with such plurals, e.g. 'just (righteous) God.'
(from Wheeler's Hebrew Syntax Notes, Copyright © 1988-2006 by Rev. Prof. Dale M. Wheeler, Ph.D. All rights reserved. Used by permission.)
I might ask your friend what causes him to look only there? In every incidence I know of, the word Elohyim translated the majority of the time as 'God', is plural, so there are at least 2000 other places to bring this up.
The true definition of the Trinity has always been a stumbling stone.
Old Joe