"To you it was shown so that you would acknowledge that the Lord is God; there is no other beside him" (Deuteronomy 4:35).
The basic faith statement of Unity is not a direct quote from the Bible—nor is it ever presented that way, as far as I know. It is a statement of what we believe to be universal Truth. The passage you cite is certainly an affirmation of that Truth. It is stated even more strongly, I think, in Deuteronomy 6:4-5, known in Judaism as the Shema, which reads "Hear, O Israel, The Lord our God is one Lord, and you shall love the Lord your God with all your heart, and with all your soul, and with all your might." And, of course, the same understanding of spiritual Truth can be found in scriptures and teachings from beliefs throughout the world.
That's why Unity is—well—Unity! We recognize and affirm universal spiritual Truth. By and large (with some exceptions) we make the choice to explore and study that spiritual Truth from the perspective of the Jewish and Christian writings known as the Bible. We also recognize and support it in other faiths—or in no faith—wherever people are joined in spiritual understanding, realizing and affirming, in one way or another that "There is only one power and one presence in the universe and in my life—God, the Good, Omnipotent."