That was the birth of unbelief

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Unbelief Does Not Hinder God

Unbelief is as old as Eden. That's where it was borned at, was in Eden. And unbelief is to doubt what God has said. Now, did you notice where unbelief was born, there was much of the Word of God considered, for Satan said to Eve… When she said, “God has said,” he did not deny that, that God had said, “so-and-so”; but he said, “Surely God wouldn't do a thing like that.” See, that was the birth of unbelief: to vary one iota from God's perfect Word. We must stay right with It, regardless of where, or what, or how, our lives and so forth must measure up with, THUS SAITH THE LORD.

Daily Bread Mark 9:24
...Lord, I believe; help thou mine unbelief.