John 11.23-25 cont.
23 Jesus said to her: “Your brother will rise again.”
24 Martha said to Him: “I know that he will rise again in the resurrection in the last day.
25 Jesus said to her: “I am the resurrection and the life; the person believing in Me will live, even if he should die.
In his letter to the Thessalonians Paul wrote: And now, brothers and sisters, I want you to know what will happen to the Christians who have died so you will not be full of sorrow like people who have no hope – 1 Thessalonians 4.13 (NLT). He was writing to a church that firmly believed in the resurrection of the dead. This was in the midst of a culture that had no such belief. This was not uncommon, even amongst the Jews there was the sect called the Sadducees who rejected the idea that the dead were to be raised.
The history of the Jews throughout the Old Testament was the belief that all the dead went to a place called ‘sheol’. This was a dismal and shadowy place of existence without hope, without joy. It was a indistinct existence. Many of the Psalms express this: For in death, who remembers You? Who can praise You from the grave (sheol)? – Psalm 6.5 (NLT).
In Job 7.9 we read:  Just as a cloud dissipates and vanishes, those who die (go down to sheol) will not come back.  They are gone forever from their home—never to be seen again – (NLT). Psalm 88 talks about those in sheol being cut off from God.
In the Old Testament there are only occasional glimpses of the resurrection from the dead: But as for me, God will redeem my life. He will snatch me from the power of death (sheol) – Psalm 29.15 (NLT). Also Psalm 73.24: You will keep on guiding me with Your counsel, leading me to a glorious destiny – (NLT).
Gradually God revealed to them the truth of life continuing after death.
In the New Testament this is fully developed, and Jesus confirms the resurrection of the dead. Especially to the Sadducees when He told them that God is not the God of the dead, but of the living.
Martha was affirming her belief in the resurrection, and that Lazarus would enter into this. Even in her grief she was not without hope, which many people lacked.
Neither are we without hope, if we trust in Jesus.
He said: 28 Do not be amazed at this, because an hour is coming in which all those in the tombs will hear His voice
29 and those who have done good things will come out into a resurrection of life, but those who have practiced wickedness to a resurrection of judgement – John 5.28-29.