Whatever has come down in the Qur’an and the Islamic traditions about Hazrat’s souvenirs is divided into two sections. Considering that the infrastructure of beliefs and deeds are effective in rectification of a society, Hazrat Mahdi (a.t.f.s.) too would rely on the infrastructures and would entrust the main foundations of his government to eminent and superior people.
The beliefs of these exalted people hold special importance. They (who are God-worshippers, pious and pure person would start their task based on real and innate values under complete training of Islam and Qur’an.
The holy Qur’an has many words about them like:
“They shall serve Me, not associating aught with Me.” (Qur’an, 24:55)
“(As for) the land, My righteous servants shall inherit it.” (Qur’an, 21:105)
“And the good end is for those who guard (against evil)” (Qur’an, 28:83)
Pondering over these verses and their likes shows that the vital souvenirs of Imam Mahdi (a.s.) would be pure monotheism, abandonment of polytheism and idol-worshipping, piety and devotion before Almighty Allah and elevation of knowledge and insight. Of course, justice at individual and social level is a natural and logical consequence of ‘Tauhid’ (monotheism) and piety.
Traditions too reckon monotheism of that era to be widespread; the message of the holy prophet (s.a.w.a.) to be global and Hazrat’s rule to be extended all over the land.
Since the diverse chains of society in forming justice and goodness are connected to one another, every part of the Islamic system is linked to monotheism, equity and piety. In other words, true belief and monotheism forms the foundation and infrastructure of good politics, welfare economy, healthy society, trained human-beings, abundant knowledge, tranquil life etc.
The below-mentioned traditions reveal the profound realities in this regard:
Imam Sadiq (a.s.) said:
“When the ‘Qaem’ will rise, no land would remain but in it the cry of ‘La-Ilaha-Illallah’ and ‘Muhammadun-Rasul’allah’ would be heard.” 
Amir-ul-Mu’minin (a.s.) said:
“…..hypocrisy, adultery, wine-drinking, and usury would die away; people would turn to devotion, divine laws, piety and congregational prayers. There wouldn’t remain any hatred against Ahl’ul-bayt.” 
Imam Baqir (a.s.) said:
“The verse: “Those who, should We establish them in the land, will keep up prayer and pay the poor-rate and enjoin good and forbid evil; and Allah’s is the end of affairs.”(Qur’an, 22:41) concerns Aale-Muhammad where Allah would bestow them with rewards of lands from the East to the West and religion would turn dominant. Through them, Allah would destroy heresy ….and there wouldn’t remain any sign of tyranny.” 
Imam Kazim (a.s.) said:
“Only the monotheists and God- worshippers would remain.” 
The holy prophet (s.a.w.a.) said:
“He will extract the treasures, divide the wealth and set firm the religion of Islam.” 
Also, the holy prophet (s.a.w.a.) said:
“….the inhabitants of earth and sky, the birds and wild animals and fishes in the sea would turn glad because of his manifestation. During his era, water would be found abundant; rivers would flow…” 
Once again, the holy prophet (s.a.w.a.) said:
“….During the end of my nation’s era, Mahdi (a.t.f.s.) will rise. Allah will quench him via rain. The earth will give out its vegetation. He will bestow wealth correctly. Fruits will become abundant. The ‘Ummah’ (nation) will turn great……” 
Verily, these are fulfillment of“Ziarate Aale-Yasin” , as we recite’:
“O Allah, make Your cites thrive and give life to Your slaves by his hands.”