English Standard Version (ESV)
If only I had seen the Red Sea part, then I wouldn't doubt God, right?
If only I had seen the manna from heaven come down every single day, then I wouldn't doubt!
If only I saw water come from a rock -- then I could be certain!
Certainty eludes us when it comes to matters of faith. We want to be sure, but it's impossible -- believing and trusting in God requires us to accept that there are things we cannot know. We tell ourselves that if we had seen certain Biblical miracles, then we wouldn't have such doubt, but the reality of the Israelites experience tells us that such memories fade, and perhaps we begin to doubt our memories. Maybe we wonder if there was another explanation, something that made more sense.
It's hard to have faith, but ultimately we are required to take a step of faith and trust in the God who we cannot wrap our minds around. God is bigger than we are, and yet he makes himself known to us through grace and love.
The key for us is to remember -- to remember what God has done, to remember what God has promised and that he always keeps his promises. Do not allow yourself to get so caught up in the stresses of this present moment that you forget about the long history of God's faithfulness and the eternal future we have with him. The challenges of a moment should not draw us into a place of doubt. Doubt can be a healthy thing, but needs to be balanced with the memories of God's faithful past and his assurances of things to come.