Read Matthew 22:23-33 here.
This is a great passage to jump off of and talk about the New Earth, the Return of Christ, etc.
But as a stand-alone sermon, I might focus on Jesus' words, "You are in error because you do not know the Scriptures or the power of God."
How many Christians live this way, to say nothing of non-believers?
People who claim to believe in God are often the biggest doubters of His Word. They don't believe the Bible stories, they don't believe miracles still happen. Jesus says flat out that they are in error because they don't believe the Scriptures or the power of God.
As Christians, it is a matter of faith for us to accept God's Word. We don't doubt it, and when we do doubt it, we try our best understand the Scripture better so that we can resolve the doubt.
The Scriptures are the only reliable source of information we have about God. Without them, we'd be clueless as to God's true nature. We can't just make up whatever we want about God or decide what we believe in the Scriptures and what we don't. We have to accept the Scriptures as God has given them to us and put our trust both in what He has said and in His invincible, still active power.