In the story of the Rich Man and Lazarus the rich man believes that a resurrection would alert his brethren to be forewarned of their fate, if they didn’t repent. Since the rich man’s sins aren’t mentioned, one sin that he may have in mind is the doctrine of the Sadducees that there was no life beyond the grave. They didn’t believe in a resurrection, so God’s blessings were to be received in one’s life on earth. There simply was nothing else. Therefore, the rich man thought his brethren needed to be warned that there was, indeed, an afterlife, and they needed to be aware of consequences of their actions.
The “truth” (so called) expressed in the idea that there is no resurrection is, since God never resurrected any man to prove there was a resurrection, there couldn’t be any kind of life after death (cf. Luke 20:27-33). Surely, a benevolent God wouldn’t permit just men to be in ignorance of something that was as important as life after death. Therefore, since there was no concrete evidence (viz. objective evidence proved through experience) of a resurrection, there must not be one. This also seems to be the argument of the rabbinic story Jesus is repeating here.
When the Sadducees came to Jesus with their question about the resurrection in Luke 20:27, he replied, showing not only their error about what life would be like in the resurrection, but also that the scriptures do, in fact, show there is a resurrection (Luke 20:34-38). Similarly, Jesus debunked the rabbinic argument in the present story, which ends with the principle that a righteous God would never permit his people to reject such an important doctrine as the resurrection, if it were really true.
Consider for a moment that the Pharisees were ridiculing Jesus’ teaching concerning the Parable of the Unjust Steward (Luke 16:14). Jesus not only debunked the rabbinic argument of the Sadducees at Luke 16:31 that there was no resurrection, but he also debunked that of the Pharisees, because they made the word of God of no effect in the lives of his people, when they taught them to obey their traditions (cf. Matthew 15:4-6; 19:3, 7). In other words, the word of God is of supreme importance, when determining what is true about our lives and what God expects of us.
In effect, Jesus’ argument in Luke 16:31 shows us that attempt of the Jewish authorities to make disciples for themselves by changing a man’s indebtedness to God (Luke 16:4-7) was labor spent in vain. It was easier to destroy heaven and earth (i.e. abolish the Old Covenant) than to take away the smallest part of God’s word, because the word of God is the very power that brought the Mosaic Covenant into existence in the first place (Luke 16:17-18; cf. Genesis 1). The logic of both schools of thought (Pharisees and Sadducees) was wanting.
The word of God, which claims there is a resurrection, is an infinitely more certain foundation for truth than an actual physical resurrection from the dead. The demand for proof (i.e. resurrect Lazarus) of proof (the word of God) is illogical. If a resurrection of Lazarus were to occur, it would not be evidence enough to change the hearts of the rich man’s brethren. This is emphasized in the fact that the Jewish authorities only dug in their heals in opposition to Jesus as they sought for an opportunity to kill him (John 11:47-53), because he resurrected Lazarus who had been dead for four days (cf. John 11:43-44)