The Sadducees had asked Jesus' opinion on a story they had made up. After all, if He could tell them parables with a meaning, surely they could do the same. Their intention was to trap Him into denying that there could be a bodily resurrection (Matthew 22:23-30). Their ruse failed as Jesus plainly told them that they did not understand the Scriptures or the nature of His eternal Kingdom.
 
So Jesus began to teach them what the Scriptures meant. He pointed to the occasion when God met Moses by the burning bush and described Himself as being (in the present tense), the God of the patriarchs, who had been long dead. The simple Hebrew grammar was not complicated and every Jew would have learned its meaning. God continues to have a living relationship with those who have died in faith. They are not extinguished from God's presence ... they are right in the middle of it!
 
God only has a relationship with living people. Yes, He knew us before we were born because he is our Life-giver and He knows us after we die if we belong to Him. The terrible thing is to be either the living-dead or the dead-dead because we have refused a relationship with Him.
 
The Sadducees were right about one thing, though. The resurrection is a pivotal doctrine. If God cannot raise the dead then the whole of our faith is mere delusion (1 Corinthians 15:12-19). But Jesus proved that God does raise the dead and that He will raise all those who believe in Him (John 6:39-40). This is such a wonderful part of the gospel message and it spurred the apostles on to keep preaching Christ (Acts 4:33). Have you ever had a discussion with friends or colleagues about what happens after death? Tell them about Jesus and encourage them to see that resurrection to eternal life is through Christ alone.