Get Proof

How to get proof:
Matthew 7:7–8 (KJV)
“Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you: For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened.”
Jesus’ words in Matthew 7 and Luke 11 are an invitation to ask, seek, and knock—persistent, personal approaching of the Father. Hebrews 11:6 says the same thing from the other side: the one who comes to God must believe that He exists and that He rewards those who diligently seek Him. Jeremiah 29:13: “Ye shall seek me, and find me, when ye shall search for me with all your heart.”
So a person who says “I will only believe if God first gives me the kind of proof I demand” is not doing what those verses describe. They are setting the terms. Scripture treats that posture differently.
The other side of the same Bible
Matthew 12:39 / 16:4 — “An evil and adulterous generation seeketh after a sign.” Jesus refused to perform on demand for skeptics who already had enough light and still would not believe.
Romans 1:19–20 — what can be known of God is already plain; they are without excuse.
James 4:3 — some asking receives nothing because the motive is wrong.
James 4:6 — God resists the proud and gives grace to the humble.
An atheist who will not even ask (“that would be circular / I need evidence first”) is often treating prayer itself as the thing that must be justified before they will use it. That is the opposite of seek-and-find.
The fair version of the point
If someone is willing to pray something like: “God, if you are there, I want to know you—show me on your terms,” that is consistent with the promise. Many people who were atheists or agnostics describe exactly that kind of asking as the turning point. The verse does not guarantee a particular miracle, a voice, or a lab result. It promises that the one who seeks finds.