The Sadducees were always out to trick or trap Jesus. They would ask ridiculous questions like if a man outlives 7 wives, which one of the seven will be his wife in Heaven. Jesus said to them that their questions was wrong because they did not “know the Scriptures.” The Sadducees didn’t believe in the resurrection of the dead. That’s why they were sad you see. (Ha – I know!) They argued that the scriptures had no teaching about life beyond the grave. Again, using the scriptures, Jesus corrected this erroneous doctrine by quoting from Exodus 3:1-6. In that passage God spoke to Moses and said, “I am the God of Abraham, Isaac, and Jacob.” In Mark 12:26, Jesus interpreted the present, indicative, active verse “I am” as proof of life after death. He said, “And as for the dead being raised, have you not read in the book of Moses, in the passage about the bush, how God spoke to him, saying, ‘I am the God of Abraham, and the God of Isaac, and the God of Jacob’?”
My old Greek Professor John Grassmick, writes, “God implied that the patriarchs were still alive and that He had a continuing relationship with them as their covenant-keeping God, even though they had died long before. This demonstrates, Jesus concluded, that He is not the God of the dead, in the Sadducean understanding of death as extinction, but of the living. He is still the patriarchs’ God which would not be true had they ceased to exist at death, that is, if death ends it all. And His covenant faithfulness implicitly guarantees their bodily resurrection.” Jesus made it clear that life after death is part of His covenant with man. He made it so and will not go back on His word.
In Mark 12:24, Jesus tells the Sadducees that they are “deceiving themselves.” Jesus is the diving Son of God that came from the great beyond and returned to it promising us a special place with Him in that place with “mansions in the sky.” Those that live solely for today with no thought for tomorrow (after life), are truly deceiving themselves. They have lost the one and only connection that will bring any real purpose and satisfaction to their lives. They things they live for under the sun; pleasure, power, possessions, will all make their life meaningless. That is Solomon’s assertion throughout the book of Ecclesiastes; it’s vanity of vanities! Solomon expresses ignorance about life after death in Ecclesiastes 3:21. He asks, “Who knows whether the spirit of man goes upward and the spirit of the beast goes down into the earth?” But he’s creating the dilemma which he will solve later at the end of the book. In Ecclesiastes 12:7, Solomon asserts his faith when he says that it’s the body that will return to dust. But the spirit which God created and is in His image will return to its creator. Jesus asserted this truth as a promise: “I go to prepare a place for you.” He adds that if this weren’t true I would never have made that promise. God’s faithfulness is not only great in this life, but His faithfulness transcends time and space into all eternity.