Irrespective of their sects, Muslims throughout the world believe that, "When Imam Mahdi (a.t.f.s.) will establish his government, peace, brotherhood, equality, justice and equity will spread to every nook and corner of the world. He will rescue the oppressed ones from the hands of the tyrants. And everybody will enjoy the bounties of the nature equally. He will establish such a government which will be free from all tyranny and evil. It will be free from war and bloodshed."

For, the aim of rising of Imam Mahdi (a.s.) will be to establish peace and equity. Holy Quran in different ways and at different places has prophesied that the pious and the weak will be the inheritors of this world. In other articles we have discussed the verses in detail.

Traditions about Justice

Holy Prophet (s.a.w.a.) in a very comprehensive and eloquent way has prophesied about the Justice of Imam Al-Mahdi (a.t.f.s.). He says
"Allah will raise a man from my progeny. He will fill the earth with justice and equity as it would be filled with tyranny and oppression."
In the initial part of this tradition he (s.a.w.a.) has assured us that before the world comes to end, it will be filled with equity and justice.

Cause of Expedience

A few questions may arise in our minds "Why is Allah delaying the establishment of a government of peace and justice? Why did He not set up a universal, just government right from day one? Why was the earth not filled with peace and justice in the times of the previous 13 infallibles? Why is this characteristic ascribed only to Imam Mahdi (a.t.f.s.)? Why did Holy Prophet (s.a.w.a.) have to prophesize this (just government) for the last period of the world?
Before answering the question, it is necessary to state that peace and justice is such a thing, that every human being loves it and strives to establish it. And the one who achieves peace and justice is the most liked person. If this characteristic is found in a governor or a leader or in his government, then such a person is considered as reliable and liked by all. This is because the love for peace and justice lies in the innate nature of man.
If we analyze human history, we will come to this conclusion, that despite liking peace and justice, till today, there is not a single instance of a leader, during whose rule this world was filled with peace and justice. Yes for a short span of time within some limits, Prophet Sulaiman (a.s.)'s kingdom was an example of peace and equality. It has been mentioned in the Holy Quran in Surah Saba, Surah Nisa, Surah Ambiya, Surah Naml, etc. that all the creatures including animals and birds, were submissive to him. Whatever he wished, like constructing a palace, masjid or cooking food, was done by the jinns before the batting of an eyelid. But even in his period, one cannot say that there was total justice and peace in the world.
Now let us try to understand why the Almighty has kept the just and equitable government for the last period of time.
Imam Baqir (a.s.) remarked, "Our government is the final government. No family will remain who has not ruled the world. But their rule shall be prior to ours. This is because they should not have a chance to say after seeing our government and principles, that if we had the opportunity, we too would have ruled the world in the same way. And this is the meaning of Allah's words, 'The end is for those who fear (Allah)'."
(Behaarul Anwaar, vol. 52, pg. 332)

Justice for Name's Sake

Our discussion revolves around the fact that justice is in the nature of man. Yet, we find that human beings are generally inclined towards injustice. In the present world, justice and equity is for name's sake. Very few people act with justice. Every group is busy in securing its own ends and even goes to the extent of trampling upon the rights of others. Even religious groups are not free from such defects. The unjust people propagate the name of justice and equity for their personal motives and the ordinary people are hoodwinked by their deceit.
We shall explain in brief the meaning of justice and then examine the Justice of Imam Mahdi (a.s.) in the light of the traditions.

The Meaning of Justice

The opposite of justice is oppression. Hence we can understand the complete justice of Imam Mahdi (a.s.) only when we have fully realized the extreme limits of oppression. The traditions quoted by us in the beginning also state that Imam Mahdi (a.s.) will fill the earth with justice and equity just like it would be overflowing with injustice and oppression (before him). Thus the vision of justice is based upon the eradication of oppression.