Some people think of the Bible as the basis of Jewish and Christian monotheism. It really depends upon your definition of monotheism. Monotheism is a modern word; it was coined in the 17th century. And it’s a contrast word to atheism, the belief that there is no god, and to polytheism, the belief that there are many gods. Monotheism is often understood as one god with a denial of the existence of other deities.
Within the biblical text, what we tend to find is much more, something that we might call monolatry, that is, the belief that there may be more deities, but that only one is to be worshipped. So, if we think of a text like the first commandment, “You shall have no other gods before me” we have a text there which allows for the existence of other deities but insists that only one is to be worshipped; Yahweh, the God of Israel.
The idea that there are no deities is found in a few biblical texts. Some texts talk about them being no gods, or nothings, or “I am the Lord; there is no other God.” The difficult question for scholars to try and work out is whether what we have there, is an ontological denial of the gods. There is no other gods; they do not exist, or whether in fact, we have here a certain form of rhetoric, a way of expressing monolatry in very strong terms that only Adonai, only Yahweh is to be worshipped and no other gods. So, do we find monotheism in the Bible? Possibly in some texts, but overall the biblical text are remorselessly monolatrous, insisting that only Yahweh is to be worshipped, and no other God.