How could the Israelites be fiercely monotheistic and yet refer to their God using the plural Elohim? First, this cannot be explained away as a “royal plural” or “plural of majesty.” Biblical Hebrew knows of no other instance in which a first-person plural is used to refer solely to the speaker.
Furthermore, while the Bible from Genesis to Revelation reveals that God is one in nature or essence (Deuteronomy 6:4; Isaiah 43:10; Ephesians 4:6), it also reveals that this one God eternally exists in three distinct persons: the Father, the Son, and the Holy Spirit (1 Corinthians 8:6; Hebrews 1:8; Acts 5:3–4). Thus, the plural ending of Elohim points to a plurality of persons, not to a plurality of gods.
Finally, although Elohim is suggestive of the Trinity, this word alone is not sufficient to prove the Trinity. Thus, instead of relying on a singular grammatical construction, Christians must be equipped to demonstrate that the one God revealed in Scripture exists in three persons who are eternally distinct.
For further study, see Robert Letham, The Holy Trinity: In Scripture, History,Theology, and Worship (Phillipsburg, New Jersey: P&R Publishing, 2004).
“Hear, O Israel: The LORD our God, the LORD is one.”