The Lord is One
“Hear, O Israel, Adonai Eloheinu Adonai is one. These three are one. How can the three Names be one? Only through the perception of faith; in the vision of the Holy Spirit, in the beholding of the hidden eye alone.…So it is with the mystery of the threefold Divine manifestations designated by Adonai Eloheinu Adonai—three modes which yet form one unity.” [1]
A Christian quote? Hardly. The above is taken from the Zohar, an ancient book of Jewish mysticism. The Zohar is somewhat esoteric and most contemporary Jews don’t study it, but there are other Jewish books that refer to God’s plurality as well.