Because Noah had faith, he was warned about something that had not yet happened. He obeyed and built a boat that saved him and his family. In this way the people of the world were judged, and Noah was given the blessings that come to everyone who pleases God.
Abraham had faith and obeyed God. He was told to go to the land that God had said would be his, and he left for a country he had never seen. Because Abraham had faith, he lived as a stranger in the promised land. He lived there in a tent, and so did Isaac and Jacob, who were later given the same promise. Abraham did this, because he was waiting for the eternal city that God had planned and built.
Even when Sarah was too old to have children, she had faith that God would do what he had promised, and she had a son. Her husband Abraham was almost dead, but he became the ancestor of many people. In fact, there are as many of them as there are stars in the sky or grains of sand along the beach.
Every one of those people died. But they still had faith, even though they had not received what they had been promised. They were glad just to see these things from far away, and they agreed that they were only strangers and foreigners on this earth. When people talk this way, it is clear that they are looking for a place to call their own. If they had been talking about the land where they had once lived, they could have gone back at any time. But they were looking forward to a better home in heaven. That's why God wasn't ashamed for them to call him their God. He even built a city for them.
Abraham had been promised that Isaac, his only son, would continue his family. But when Abraham was tested, he had faith and was willing to sacrifice Isaac, because he was sure that God could raise people to life. This was just like getting Isaac back from death.