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Isaiah 43

2. When thou passest through the waters, I will be with thee; and through the rivers, they shall not overflow thee: when thou walkest through the fire, thou shalt not be burned; neither shall the flame kindle upon thee.

"neither shall the flame kindle upon thee," The fire won't even be able to use you as a source of fuel, it won't do any kind of damage to you.
I can kind of see this too as someone who is able to reside in "eternal burnings"