The Danger of Unbelief

There are a lot of things the book of Hebrews could have told us to watch out for that would hinder us receiving the promises of God---but what happened to the first generation of Israelites that were delivered from Egypt is what we are warned to watch out for. From the foundation of the world, God had a land, hand-picked and prepared for them. It was the plan of God--the will of God--for these people to go into this specific land--at this specific time--yet they failed to do so. They had already come through a lot of adversity and hardship and they were so close---what happened?