During the time of the Mahdi (May Allah hasten his blessed advent) our Holy Prophet and our infallible Imams (Peace be on them) will return to this world along with a body of men belonging to the past and the subsequent nations, with a view to demonstrate their power and establish their rights. This is what has been expressly mentioned by a number of continuous reports and Qur'anic verses. Allah says:
The day on which We will assemble a group from every people.
Therefore it is obligatory to believe in the doctrine of 'Return' (raj'ah).1