God offers to be our Saviour and explains he's the only one in Isaiah 43. Anyone who doesn't believe in God needs a Saviour to save them from the horrors to come, if it takes believing Jesus came from God, then as the Christians believe you're saved. If you believed the childhood stories about Noah or Moses and still do. I personally wouldn't think you'd need one.
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You are my witnesses,” declares the Lord,
“and my servant whom I have chosen,
so that you may know and believe me
and understand that I am he.
Before me no god was formed,
nor will there be one after me.
11 I, even I, am the Lord,
and apart from me there is no savior.
12 I have revealed and saved and proclaimed
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God was the God of only the Jews but they polluted the relationship and God has hid his face from them. So God offered his Servant in Isaiah to the all the Peoples of the World and is willing to make a Covenant with them who believe. It’s all laid out there in Isaiah 42 & on.
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The Jews wait on a Messiah who is described in Isaiah also.