Isaiah 58
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Isaiah 58:6a "Is this not the fast which I choose…”
So, if God says that today He wants you to fast for someone, you can expect that God is about to do something.
There is a guarantee that God’s words will go out, and accomplish what He wants. In Isaiah 55:11, it says that His word will go out and not return empty, and will accomplishing what He desires.
When you decide on your own to fast for whatever reason, you can be hopeful that something might happen, but, there is no guarantee.
Prayer coaching. “Jesus, do you want me to fast today for someone? Make it clear to me that you want me to fast for them.”