In the name of God, the beneficent, the merciful.
Islam is the Continuity and complementary religion of all Abrahamic religions. A well-known expert in study of religion, named as “John Boyer Noss”, calls Islam as “the Monotheistic religion” in his book, A History of the world’s religions.
Now a question rises of the use and result of the Monotheistic religion for human beings?
As a matter of fact, there is a substantive difference between a monotheistic point of view and other views. Quran explains it so clearly:
زمر 29“ضرب الله مثلا رجلا فیه شرکاء متشاکسون و رجلا سلما لرجل هل یستویان مثلا”
“God gives an example of a slave who has several incompatible and disagreeable masters, compared to another who has only one master. Do these two slaves have the same condition?” (zumar,29)
To look at the world having a unique and only center, which is the source of all goods and perfections, will change the human beings attitude in a way that cannot be described well.
This monotheistic point of view gives the believer a pure sense of devotional freedom and independence, and the believer is just the slave of God and is free from anything else.
Imam Ali (as) draws the lines of this freedom so beautifully saying that:
(نهج البلاغه نامه 31)“ لا تکن عبد غیرک و قد جعلک الله حرا”
“For sure, God made you be free, don’t be the slave of anyone else, but him.” (Nahjul-balaghah, letter 31)
This freedom is something in his mind and spiritual, even if his hands are tied:
فاش می گویم و از گفته خود دلشادم
بنده عشقم و از هر دو جهان آزادم (حافظ شیرازی)
“I say aloud and I feel so happy to say that, I am the slave of God’s love and free from anything else!” (Hafiz)
It merits mentioning that a believer’s freedom is not as opposed to the other people’s right of freedom. His freedom is dependent on the satisfaction of the creator of the world. The creator who is not an oppressor, nor he likes the oppressors. Thus the monotheistic believer does not allow himself to act injustice in anyways. He sees himself responsible to the whole world; not only the other people, but also any possible living creatures on the earth; a knowingly, consciously, and wisely responsibility in the light of the divine teachings.
It is because he sees every single creature as an act of God.
From this point of view, the morality has a completely different function which is so beyond all moral systems.
Hence, this religion would have a perfect moral system based on the monotheistic core and point of view. That is why the great prophet Mohammad p.b.u.h clarifies the main reason of his mission as a prophet, to complete the criterion and standard of morality. (Bihar-ol-anvar, 68, 382)
(بحار الانوار ج 68 ص 382)“انما بعثت لاتمم مکارم الاخلاق”
Morality would be in its highest level, when it is practiced in the light of devotional freedom.
We believe in a God who does not oppress anyone at all (younos,44):
لا یظلم الناس شیءا (یونس 44)
And who is the most justice and the most merciful and gave values to the man kind (Isra,70),
و لقد کرمنا بنی آدم (اسراء 70)
Indeed, God orders to observe justice and being kind to one another (Nahl,90),
ان الله یامر بالعدل و الإحسان (نحل 90)
And prevents from obscene acts and rebellion,
و ینهی عن الفحشاء و المنكر و البغی … (نحل 90)
Therefore, the more being pious, the more precious in the God’s eyes (Hojorat,13).
ان اکرمکم عند الله اتقاکم (حجرات 13)
and piety is nothing but avoiding oppression to self and to others.
At the end, I would like to draw your attention to the fact that why there were many people, like Soheib who was Christian, Salman who was Persian, Belal who was a black slave, and many others from all over the world with different races and religions, fell so deeply in love with Mohammad p.b.u.h and followed him?
This story is just an example of how Prophet Mohammad p.b.u.h treated with people from other religions than Islam with dignity:
the agreement between the Holy Prophet of Islam (peace be upon him and his family) and the Christians who were resided in the land of Sina:
“In the name of Allah, the beneficent, the merciful.
This agreement is written by Mohammad, who is good tidings and deterrent, and who is the trustworthy and honest in the divine trust for all the creatures of the world. And God is the most esteemed and the most Sage.
Mohammad has wrote this agreement to his followers to agree upon it with all Christians in east or west, close or far away, Arabs or any other nationalities, those who are known or unknown.
All Muslims who invade this agreement did disobey the rules of God, they would not consider being righteous and deserve to be cursed; whether to be a king or an ordinary Muslim.
We Muslims, will be the guardians and protectors of any Christians who is anywhere inside the Islamic lands, and I will defend them and their properties with my own life and with the lives of my all followers and companions; because they are like my own people and we are the ally. None of their priests, their gatherings, their worships, and their people is allowed to be invaded, and it is not allowed to destroy their churches or temples. The Christian priests and Judges are free from paying ransom, and others should not pay more than normal amount. None of them should be forced to participate in wars; instead they should be protected by Muslims and should be treated with dignity according to the verse saying:
وَ لا تُجادِلُوا أَهْلَ الْکِتابِ إِلاّ بِالَّتِی هِیَ أَحْسَنُ (عنکبوت 46)
“Don’t talk to the followers of other divine religions, but in the best way of treatment.”(Ankabout, 46)
They deserve to live in a place full of kindness and peace and anywhere they decide to live in, this peaceful condition should be guaranteed for them.” 
This is what the holy prophet Mohammad p.b.u.h aims by his mission from the God, to spread the values of moralities and to invite the entire God’s creatures to come to a united and perfect way of life.
This is how he unveils the true morality, based on the divine thoughts and teachings, and guides his followers and all the people of the world through the bright way of Monotheism and seeking the satisfaction of the only God by respecting to all His people and observing their rights.
That is why we can divide the history of the world into two parts:
The world before Mab’ath, and the world after it.
اللهم صل محمد و آل محمد و صل علیه صلوة لا غایة لعددها و لا نهایة لامدها و صل علی جمیع الانبیاء و المرسلین
O Allah, bless Muhammad and his family, the way that there would be no end to it. And bless all other holy prophets and messengers.
 عمید زنجانی، عباسعلی، حقوق اقلیت ها، (تهران: دفتر نشر فرهنگ اسلامی، 1362، چاپ سوم)، صص78 ـ 76 ; از سیره ابن هشام، ج2، ص902