John 17:3

and this is life eternal, to acknowledge thee to be the only true God, and Jesus to be the Messiah whom thou hast sent.

Mark 12:29-32

Jesus answer'd him, the first of all the commandments is thus deliver'd, "hear, o Israel, the lord our God is the only lord.

1 Timothy 2:5

for there is but one God, and but one mediator between God and men, the man Christ Jesus,

John 10:30

I and my father are one.

1 Corinthians 8:4-6

As to the eating therefore of what is offered in sacrifice to idols, we know that the heathen deities have no real existence, and that there is but one God.

Treasury of Scripture Knowledge

Summary

Hear, O Israel: The LORD our God is one LORD:

General references

Bible References

General references

James 2:19
you believe there is but one God, very well: the demons believe as much, and tremble."