Just like today, the Jewish people in the time of Jesus were divided over varying beliefs about their faith. One of the biggest questions was whether there will be a resurrection of the dead at the end of the world. The Pharisees said yes and the Sadducees said no. It was with this debate in mind that the Sadducees approached Jesus to find out His position on the topic, hoping to trip Him up. However, in His usual fashion, Jesus turned the question around on them by pointing out that their question was really unnecessary. When we get to heaven, we will not be concerned with who we are married to because, like the angels, we will be in the presence of God and that will be our focus.
He then begins to discuss the question of the resurrection of the dead. This is the source of our belief as Catholics that the dead are not truly dead, but have instead just moved on to eternal life with God. As Jesus says, our God is a God of the living, not the dead. This is something we sometimes forget. Our loved ones who have passed away are not just lying in a grave somewhere. They are still alive and active, just, as Fr. Mike says, "On the other side of eternity." This is why we are still able to pray both for them and ask them to pray for us. This is what we mean when we talk about the "Communion of Saints." It is all Christians who have ever lived united together as the Body of Christ.
While this thought is meant to comfort us, it can be difficult at times since the person is no longer physically with us. That is why the Church provides us with these readings, to remind us of these truths that Jesus has shared with us. Especially during this time of the year, when it seems like everything around us dying and going to sleep, the Church in her wisdom reminds us that this is not the end. There will be a spring. There is a reason to hope. Christ has conquered death and opened the gates of Heaven. If we truly believe this, we can take comfort that one day we will be reunited with those we love. What a great sign of God's love for us, His children!