From Islamic traditions, it can be inferred that this issue is confined to those righteous believers, who possess an elevated rank with respect to their faith, and similarly disbelievers, who are placed at a low-grade rank with respect to their disbelief. It appears that the return of these two groups into the world is for the purpose of completing a circle of perfection in the case of the first group and tasting worldly chastisement regarding the second group.
The wisdom of Allah (s.w.t.) necessitates that the group of sincere believers - who, in their journey towards spiritual perfection, had come across obstructions in their life due to which their development had been left incomplete - continue their journey towards perfection by being brought back into this world. They shall then witness the universal government of truth and justice, and participate in the establishment of this system. This is because participation in the establishment of such a government is one of the greatest distinctions (for man).
On the contrary, the group of obstinate tyrants, apart from their special chastisement on the Day of Judgment, should also be punished in this world like the punishment tasted by obstinate nations such as 'Ad, Thamud, the people of Fir'awn and Prophet Lut (a.s.), and the only way to accomplish this is by means of raj'at.
In a tradition, Imam as-Sadiq (a.s.) says:
إِنَّ الرَّجْعَةَ لَيْسَتْ عَامَّةٌ وَ هِيَ خَاصَّةٌ، لاَ يَرْجِعُ إِلاَّ مَنْ مَحَّضَ الإِيـمَانَ مَحْضاً أَوْ مَحَّضَ الشِّرْكَ مَحْضاً.
“Surely the raj'at is not universal, but specific; only those shall be returned, who are downright pure in faith or downright pure in polytheism.”1
It is possible that verse 95 of Suratul Anbiya, which states:
وَ حَرَامٌ عَلى قَرْيَةٍ أَهْلَکْنَاهَا إِنَّهُمْ لاَ يَرْجِعُونَ
“And it is binding on a town which We destroy that they shall not return)” is also an allusion towards this meaning. This is because the issue of non-return is stated in connection with those, who have tasted their punishments in this world; thus, it becomes manifest that those, who have not witnessed their punishments, ought to return and taste it.
Another possibility that exists is that the return of these two groups in that specific phase of human history is to present before mankind two important signs - the power of Allah (s.w.t.) and the issue of Resurrection (the Origin and the End) - in order that by witnessing it they reach the zenith of their faith and spiritual perfection, and do not possess any kind of shortcoming.2