The Corruption of Previous Revelations:
A lot of modern academics believe that the Torah (the Old Testament) or the Hebrew Bible, as we have it now, the written form of it, cannot be traced back to the Prophets.
The Torah and the Injeel (New Testament) are the 2 fundamental revelations. When Musa (alaihissalam) when to the top of the mountain to speak with Allah (subhanahu wa ta’ala), Allah (subhanahu wa ta’ala) said, “the hour is coming, I’m keeping it almost hidden, so every single person can be given according to whatever effort he/she made”. It was one of the first teachings given to Musa (alaihissalam).
Diverging Beliefs Among the Jews:
When we look at Jewish tradition and go back a few centuries, even before Isa (alaihissalam), we will discover that the Jews were broken up into 2 major groups – Sadducees and the Pharisees.
Sadducees
The sadducees were the custodians of their qibla (Jerusalem). They were religious people – they did rituals and worship. They believed their entire religion is focused on the worship of the temple and sacrifices in front of the temple. They didn’t believe in an Aakhirah. They believed we would be turned into dust.
Pharisees
The Pharisees believed in a resurrection. They also believed in a part of Torah that was not written. It was only transmitted orally i.e. it was recited and passed down. Although they did believe in an Akhirah, they believed that the nations will be judged and not individual people. This is completely different from what Musa (alaihissalam) was given. So, a lot had changed over the centuries.
When the temple was destroyed and the Jews were exiled, historians argue that the Sadducees were completely wiped out and the only ones that were left were the Pharisees, who had some weak concept of Akhirah. When we look at the Hebrew Bible there is no mention of Akhirah, Jannah, Naar (Fire) etc. which is such a central concept in the Quran.
The Survival of the Afterlife Concept:
By the will of Allah (subhanahu wa ta’ala), some of this concept somehow survived in oral tradition and made its way back a couple of centuries before Isa (alaihissalam). Slowly some groups of Jews started believing in the afterlife again. In the Bible (New Testament) from whatever record we have, Isa (alaihissalam) actually debates with the Sadducees about Akhirah.
The Forgotten Belief in the Afterlife:
The fundamentals of our religion are belief in God, belief in revelation and belief in afterlife. Of these three, the belief in akhirah was forgotten or completely corrupted by them.
Reviewing this ayat again, ‘what was sent to us and what was sent before us’ includes belief in God, stories of Prophets, laws etc. But of all things, Allah (subhanahu wa ta’ala) highlighted the afterlife by saying that, when it comes to afterlife, the people of taqwa have absolute conviction.
When the Jews and Christians came to this book, the thing that hit them like no other was Akhirah, because it was completely forgotten in their traditions.
Life as a Preparation for the Afterlife:
One of the goals of a student of the Quran is to understand how everything Allah (subhanahu wa ta’ala) teaches in the Quran in one way or the other takes us back to that meeting with Allah (subhanahu wa ta’ala). This life is about getting closer to Allah (subhanahu wa ta’ala), the next life is when you get ultimately close. So, this life is actually a preparation for the next one where we actually have to meet with him – every salah is a rehearsal for judgement day, every Jumuah is a gathering like the day of gathering, Hajj is a rehearsal for standing in front of Allah (subhanahu wa ta’ala) like we stand on judgement day. Every act of worship in one way or another reminds us of standing in front of Allah (subhanahu wa ta’ala).