“Come now, let us reason together, says the LORD:
though your sins are like scarlet,
they shall be as white as snow;
though they are red like crimson,
they shall become like wool.
If you are willing and obedient,
you shall eat the good of the land;
but if you refuse and rebel,
you shall be eaten by the sword;
for the mouth of the LORD has spoken.”
 
Isaiah 1:18–20 (ESV)
 
If you want to know that "the LORD He is God! the LORD, He is God!" (1 Kings 18:39) your search for confirmation finds its best resolution in the book of Isaiah. I would argue that Isaiah, more even than Elisha, "wore the prophetic mantle" of Elijah. Only John the Baptist was a greater merely human incarnation of the role of prophet (Matthew 11:11).
Isaiah 42:9 tells us: "Behold, the former things have come to pass, and new things I now declare; before they spring forth I tell you of them.”
Below find two articles that discuss fulfilled Old Testament prophecies. By any objective measure, only God could do this.
As with other books of the Bible, we suggest this brief overview of Isaiah. May your listening to this great OT prophet be as blessed by God as was our reading of it!
 
https://youtu.be/d0A6Uchb1F8?si=Nhsvg2DCZgWRZq_7
 
Check out these two articles on calculations of the probability of one first-century man, Jesus, fulfilling so many OT prophecies!
https://nickcady.org/2020/02/18/the-statistical-probability-of-jesus-fulfilling-the-messianic-prophecies/
https://firmisrael.org/learn/how-many-messianic-prophecies-did-jesus-fulfill/#:~:text=After%20all%2C%20Jesus%2

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