When the seraph touches Isaiah's lips with the burning coal in Isaiah 6, the word the text uses for what happens next is from the root kaphar כָּפַר. The same root as Yom Kippur. Atonement. Cover.

The coal doesn't scorch Isaiah into silence. It covers him. Cleanses him. Makes him fit to speak what he couldn't have spoken with unclean lips.

And then immediately God says whom shall I send. The cleansing and the calling happen in the same breath. God doesn't wait for you to feel worthy. He makes you worthy and then hands you the assignment in the same moment.

Isaiah didn't volunteer from a place of confidence. He volunteered from a place of fresh atonement. There's a big difference and it matters so much.

Here am I; send me.