In Isaiah 38:7-8, God gives Hezekiah a sign that he will heal Hezekiah and add 15 years to his life. This is a supernatural event. It’s a miracle. The sun cast a shadow on the dial and as the shadow moved with the declining sun, it would show the passing of time. God’s sign to Hezekiah was to make the shadow cast by the sun move backwards.
So how did God do that? We don’t know exactly how it happened because the Bible doesn’t tell us. God could have stopped the world on it’s axis. Or it could have been a refraction of light. Whatever the miracle was, it was a miracle because it happened at the moment God wanted it to happen to coincide with his purpose in the life of Hezekiah.
Do you believe this really happened? Maybe you're not a Christian yet or you're not sure what you believe. Or maybe you've recently trusted in Christ and you're trying to understand better the ways God works in the world he's made. Either way, you might not really be sure whether it’s reasonable to believe that this miracle actually happened the way the Bible describes it. And I understand that.
We all assume certain things about the world. We all have commitments, values, and beliefs that are like lens through which we see the world. And one of those lens is our assumptions about God.
If you already presuppose that God doesn’t exist — or maybe if he does exist he’s absent from the world — then of course it’s more reasonable to say that miracles don’t happen. If God doesn’t exist the world is entirely impersonal. The universe is made up of matter, energy, and motion that operates according to observable scientific regularities and there are no exceptions, i.e., there are no miracles. So miracles in the Bible have to be seen as untrue. And people will say that they’re religious myths and that it’s irrational for a modern person to believe them.
But the Bible gives us a completely different view of the world. The Bible tells us that God does exist. And not only does He exist, but He personally created the world and even today continues to rule it. Moreover, it’s the creating and sustaining power of God’s Word that keeps the laws of matter, energy, and motion working in ways that we can measure and observe.
Because God is a personal God, He acts in the world to accomplish his own purposes. The Bible tells us that we live in a personal universe where God cares about us as persons. If we accept what the Bible teaches us about God, then exceptions can happen. Miracles fit rationally with God's purposes in the world.
So when we look at this miracle God performs of causing the shadow to move backwards as a sign for Hezekiah, it's not some weird thing that happens. God tells us why he decided to make an exception to the way He normally operates the world. And it’s rational for Him to do a miracle when we decides to for his own purposes. It's an expression of His faithfulness to His people.