What would have happened to Noah if he had believed a flood was coming but never built the ark?
If Noah had only believed a flood was coming but never built the ark, he would have been washed away right along with the rest of them. His faith had to be accompanied by the action of building the ark; belief alone would not have saved him from the judgment.
Les explains from Hebrews 11:7 that Noah, being warned by God of things not seen as yet, was moved with fear and built an ark. He did something. Les then asks what would have happened if Noah had stood in the Middle East and said, “I believe a flood is coming,” but never built the ark. The answer is that he would have gotten washed away with the rest. Along with his faith that a flood was coming, Noah built an ark. This illustrates faith joined with obedient action, unlike Abraham, who simply believed God and righteousness was imputed to him without his doing anything.
By faith Noah, being warned of God of things not seen as yet, moved with fear, prepared an ark to the saving of his house; by the which he condemned the world, and became heir of the righteousness which is by faith.