Commenting on the nonsensical argument that elohim “proves” that God is uni-personal, Anthony Buzzard and Charles Hunting correctly noted the following:
An occasional anomaly proves as little as the fact that Joseph’s master is described by a plural noun several times (Ge. 39:2, 3, 7, 8, 19, 20). Will anyone contend that “Joseph’s mater [plural in Hebrew] took [singular verb] him” is incorrectly translated? Abraham is the “masters” (plural in Hebrew) of his servant (Gen. 24:9 10). Is there plurality in Abraham? No one would want to alter the translation of another passage in Genesis: “The man who is lord of the land spoke harshly to us.” But though the verb is singular the noun has a plural form, “the lords of the land” (Gen. 42:30). (Anthony F. Buzzard and Charles F. Hunting, The Doctrine of the Trinity: Christianity’s Self-Inflicted Wound [Lanham, Md.: International Scholars Publications, 1998], 272)
While I disagree with Buzzard on many issues (e.g., his rejection of the personal pre-existence of Jesus), he and his co-author are spot-on in their refutation of this nonsense "argument" for the Trinity. To be fair, many Trinitarians reject this argument, including Gregory A. Boyd. Under the heading of "Weak Arguments for the Trinity," Boyd wrote the following in his book critiquing the theology of Oneness Pentecostals:
[I]t is not uncommon to find Trinitarians arguing for the doctrine of the Trinity on the basis of the fact that the word for God in the Old Testament is Elohim, which is the plural of the word El. Hence, it is thought to imply a plurality in the Godhead.
Unfortunately, this is indeed, as most Hebrew scholars recognize, a very weak argument on which to base the doctrine of the Trinity. When a numerical plurality is intended, the corresponding verb(s) in the context will be plural. When the one true God is referred to as Elohim, however, the corresponding verbs are always singular. Moreover, as Bernard [a Oneness Pentecostal Boyd is responding to], the term is applied to the one angelic being who wrestled with Jacob (Gen. 32:30) and to the one golden calf the Israelites worshipped (Exod. 32:1, 4,8) (Bernard, Oneness, 147) . . . Even weaker is the argument that the Hebrew word for “one” “(echad) used in the Shema (“Hear O Israel, the Lord our God is one Lord”) refers to a unified one, not an absolute one. Hence, some Trinitarians have argued, the Old Testament has a view of a united Godhead . . . [notwithstanding] one cannot at all base such a view on the Godhead on the word itself. (Gregory A. Boyd, Oneness Pentecostals and the Trinity: A World-Wide Movement Assessed by a former Oneness Pentecostal [Grand Rapids, Mich.: Baker Book House, 1992], 47-48; comments in square brackets added for clarification)