'Proof' in the Bible

He named the place [where this miracle occurred] Massah (test) and Meribah (contention) because of the quarreling of the sons of Israel, and because they tested the [patience of the] Lord, saying, “Is the Lord among us, or not?”

“Ask a sign for yourself from the Lord your God [one that will convince you that God has spoken and will keep His word]; make your request as deep as Sheol or as high as heaven.”