The belief in the return is not a fundamental part of the doctrine. It is an idea mentioned in some narrations. These narrations say that at the end of time, people will come out of their graves. This includes both believers and disbelievers. It will happen when Imam Al-Mahdi (a.s.) is about to appear. They will fight again. Belief will win over falsehood.
We do not accept these stories. We reject them from the point of view of their references. We also reject their content. We do not believe in the return in the way that has been explained. Not believing in this idea does not make one desert Islam. It does not make one desert Shiism.
We believe, as stated in the Glorious Quran, that Allah is capable of bringing the dead back to life. However, this concept of a specific return is something else.
The concept of return is evident in many narrations. But there is confusion in their content. They are confused in defining what is meant by it. This makes the talk about the return of specific people unreliable. Therefore, the return of the state and rule of the right is more probable. This would be through the appearance of Imam Al-Mahdi (a.s.). It would be the establishment of justice after oppression and tyranny.
The narrations about the return are confused. They discuss the return of certain people. This means the return in general is proven. However, it is not proven as the return of certain specific people. It is possible that they refer to the return of the state of the right.
Ash-Sharif Al-Murtada mentioned that some of our companions interpreted the return as the return of the state. It is the return of enjoining good and forbidding evil. It is not the return of persons or the bringing of the dead back to life. He did not approve of this opinion. But he said that the return of people has not been proven by the apparent meaning of the stories. Its proof is based on the consensus of the Imamis on its meaning. This consensus might be conceptual, as it is based on confusing narrations. Therefore, one must go back to study the content of these narrations.
Imam Al-Rida (a.s.) quotes the Messenger (p.) as saying: "Islam began as something strange, and it will return to being strange, so good tidings for the strangers." He was asked: "Then what?" He said: "Then the right will return to its owners."