Every time I have read Job chapters 38-41 I always think of how those words are so humbling and that it shows how magnificent, powerful and wise God truly is. We see God Himself actually speaking directly (audibly) to Job. Imagine you and your friends talking about God and saying He's not real or saying anything untrue about God then all of a sudden you hear these words spoken by God Himself, "Who is this that darkens counsel by words without knowledge? Brace yourself like a man; I will question you, and you shall answer me" Job 38:2-3. I mean if I had heard that I might have fallen back straight to the ground like the soldiers in the Garden of Gethsemane after Jesus said "I am He" in response to them saying they were looking for Jesus of Nazareth. (story found in John 18:1-12)
The very questions God asks in Job chapters 38-41 no know-it-all can answer. I love when God asks, “Where were you when I laid the earth’s foundation? Tell me, if you understand. Who marked off its dimensions? Surely you know! Who stretched a measuring line across it? On what were its footings set, or who laid its cornerstone while the morning stars sang together and all the angels shouted for joy? " Job 38:4-7 and when He asked, “Have you commanded the morning since your days began, and caused the dawn to know its place?" Job 38:12. Who can answer that? Which human being can stand before God and say they have or can point out who has done those things? Even as a Christian who actually believes in God, what God said in those chapters is so humbling.
Who would dare to challenge the living God? Well, many atheists and others who don't believe the Gospel of Jesus Christ attempt to do it daily. I just watched some testimonies with several atheists who came to believe the truth about God, but one interview in particular stood out to me with former atheist Peter Hitchens . Peter said , "One of my reasons for the change in my view of this is that I am scared, but then again the fear of the Lord is the beginning of wisdom." Yes, "the fear of the Lord is the beginning of wisdom" as written in Proverbs 9:10 and Proverbs 111:10.
God isn't speaking to us today with an audible voice out of a whirlwind like He did in Job chapters 38-41, but He does speak to us through His Son Jesus Christ (Hebrews 1:1-2) and that is done through His words in the Bible. If we reject the word of God we have also rejected Jesus His Son and if a person rejected the Son of God they have rejected God because the two are One as Jesus Himself has said in John 10:30, "I and the Father are one.” and what He explains in John 12:46-49 "I have come into the world as a light, so that no one who believes in me should stay in darkness. If anyone hears my words but does not keep them, I do not judge that person. For I did not come to judge the world, but to save the world. There is a judge for the one who rejects me and does not accept my words; the very words I have spoken will condemn them at the last day. For I did not speak on my own, but the Father who sent me commanded me to say all that I have spoken." and John explains in 1 John 2:22-23. "Who is the liar? It is whoever denies that Jesus is the Christ. Such a person is the antichrist—denying the Father and the Son. No one who denies the Son has the Father; whoever acknowledges the Son has the Father also."
The counsel I would give anyone denying the existence of God or denying Jesus Christ as the Son of God is this, humble yourselves. God will give mercy and grace to you if you humble yourselves (James 4:6), believe the Gospel of Jesus Christ and repent while you still have time (Acts 16:30-31).
You must be born again (John 3:1-21), meaning born of the Spirit of God after you have confess your sins (admit you are a sinner), Repented of your sins (turn away from your sins, meaning stop doing them, instead of doing evil, bad, wrong, choose to do what is good in the sight of God), Believe in the Gospel of Jesus Christ which is Good News. It is good news because of this: since the wages of sin is death (Romans 6:23) and we ALL are sinners (Romans 3:23) we deserved death BUT God in Christ Jesus paid that price for us with His life so we wouldn't have to, He did that because He loves us. God came in the flesh (Jesus Christ ) meaning God actually became a human being and laid down His life for us so we could be reconciled to Him as mentioned in 1 Timothy 3:16. He was delivered to death for our sins, but He was resurrected for our justification (Romans 4:25). God not only does that but He also supplies believers with His Holy Spirit who teaches us the truth and comforts us and helps us to resist sin and He helps us to walk in God's ways if we obey God (John 14:25-27). God didn't give us all this time for people to go about denying His existence and blaspheming His name and living is sin. God has given us all this time for people to repent of their sins, (2 Peter 3:9). We ALL must believe the testimony He has given of His Son Jesus Christ which is that we have been given eternal life and that is through Jesus Christ the Lord, (Romans 6:23, 1 John 5:9-12).