As explained in the first part of the topic, Islam has spread much more quickly compared to other religions all over the world. The traits of Prophet Muhammad (PBUH&HP) were introduced as one of the reasons. Here, the effect of the scientific and social interactions with the rest of the world throughout the Islam's history is discussed. 

 As an introduction, it is good to know that Islam has adopted two types of regulations; confirmed rules and established ones. The Islamic approach regarding the confirmed rules -the regulations which existed before and were conserved or revised if needed- is one of the keys to the development and permanence of Islam. And, this will be the focus of this article.   

Saying Yes to the Good Costumes throughout Islam's History

The Islamic approach to the habits and rules that were common in the pre-Islamic era was that it neither opposed them totally nor accepted them entirely. In some cases, Islam has affirmed and preserved some rules. That was when those rules or customs were not in contradiction to the social order and the living facilities of humans or in case of the righteous customs and traditions that existed before the emergence of Islam; e.g., some of the rules on making contracts. 

However, some of the useful regulations required to be revised and this was accomplished by adding some conditions. On the contrary, some customs and routines were opposed and removed due to the bugs and disadvantages or because they were manipulated or misused for personal benefits; e.g., usury (Riba) [1].

The rules conserved by Islam, such as those about the ownership and property, are called confirmed rules. On the other hand, the rules instituted by the Islamic jurisprudence which never existed before are called established rules [1]. This demonstrates that Islam has always been in constant interaction with the world, and the positive aspects of human societies are considered. Hence, the message of Islam and its framework have not been far from what people are familiar. This consequently has made it easier to accept Islam.

Seeking knowledge; A Way to Spread Islam

Islam has urged everyone to seek knowledge. The first verse of the Quran revealed to Prophet Muhammad (PBUH&HP) enjoined reading which is the key to knowledge: “Read in the Name of your Lord who created” (96:1). Literacy and having knowledge are so important in Islam that Quran equals illiteracy to being in darkness. According to Prophet Muhammad (PBUH&HP), seeking knowledge is obligatory (Wajib) for every Muslim and God loves those who seek knowledge [2].

Learning and seeking knowledge have been emphasized such that Muslims have been encouraged even to travel in order to learn things. Imam Ali (AS) recommended traveling to acquire privilege and named gaining knowledge as one of the achievements of traveling [3]. Prophet Muhammad (PBUH) advised seeking knowledge even if for that purpose one should go to the lands far away [4].

The Holy Quran also addresses the believers as those who are not affected by the wrong behaviors of others since they have been guided. So, the believers can peacefully learn from the positive aspects of others. Another proof of the attention paid to knowledge in Islam is that Muslims used to release the prisoners of wars who taught literacy to a certain number of Muslims. All these emphases and recommendations have urged Muslims to travel to gain knowledge. As a result, Muslims who traveled to other places and countries were practically the messengers of Islam there, which, in consequence, accelerated the spread of Islam.

Continuous interaction with the world During Islam's History 

The actual advances all over the world are the outcomes of the efforts that various nations and civilizations have made in the course of time, among which are the Islamic civilizations [6]. Muslims in different countries, like Spain and Italy, have always been in interaction with other people; therefore, they could transfer the Islamic civilization and culture to others and also receive from them. As an instance, in the battle of the Trench (Khandaq), Salman Farsi proposed to dig a trench around Medina.

This was a tested strategy in Persia, and Prophet Muhammad (PBUH&HP) accepted it. Many of the important Arabic resources and books were translated into European languages, some of which were later on taught and used as references in scientific centers in non-Muslim countries. The bonds between Muslims and Christians through marriage [i] and social relationships were of other means to expose non-Muslims to Islam [7]. All these factors have helped the quick spread of Islam.

From what has been discussed, we can see that the Islamic approach of making regulations under the form of confirmed rules, the encouragement to obtain knowledge and literacy, and cultural exchanges with the rest of the world played significant roles in attracting many savants and people to the religion of Islam.    

Notes:
[i] This kind of marriage named Interreligious marriage is permitted in Islam under the certain conditions. 

References:

1. spreading Islam
2. “Misbah al-Shariah”, p. 13.
3. M. Nuri, “Mustadrak al Wasail”, vol. 18, p. 115.
4. “Misbah al-Shariah”.
5. “Ghurar al-Hikam wa Durar al-Kalim”, p. 46, T. 188.
6. history of Islam
7. A. Velayati, “Dynamism of Islamic and Iranian Culture and Civilization”, vol. 1. 

Coexistence means living together, cooperating socially and economically of either the people of two countries to fulfill their livelihood or two individuals who might not share the same interests. In other words, coexistence includes being together, not interfering in others’ private affairs, and respecting the rights of others. Islam, which considers both the individual and social needs of human beings, offers a complete package for a thriving social life. Through its teachings, the Prophet’s (PBUH & HP) and infallible Imams’(AS) tradition (Sunnah), and the Quranic teachings, Islam has provided some clear guidelines for Muslims and the followers of other religions peaceful coexistence in the Quran. Here, we focus mostly on what the Quran offers in this regard. 

1. Justice and Beneficence in Dealing with Others for A Peaceful Coexistence in the Quran

The first point raised about the peaceful coexistence in the Quran is that Muslims should deal with non-Muslims with justice and beneficence, as far as non-Muslims have not expressed any hostility against them and don’t respond to their kindness with hatred (60:8). In Surah Mumtahina, it is said that: “Allah forbids you only in regard to those who made war against you on account of religion and expelled you from your homes and supported [others] in your expulsion, that you make friends with them, and whoever makes friends with them—it is they who are the wrongdoers.”(60:9). 

Accordingly, non-Muslims are in two groups — the first group who are in peace with Muslims and live peacefully with them. The Islamic government and Muslims of society should respect this group and recognize their rights. The second group is those who act against Muslims, Islam, and the Islamic government. Undoubtedly, they should be counteracted, and there would be no place for peace in this case [1]. That’s why Imam Ali (AS) had devoted a share of public treasury (Bayt al-mal) to help the needy people of other religions. It means that an Islamic government does not overlook non-Muslims, but recognizes their rights and supports them. (10:57) 

2. Recognizing Freedom of Thought is an Underlying Factor in Muslims Peaceful Coexistence in the Quran

Humans naturally tend to reject any imposed idea or belief. And, the Quran never orders something which opposes to human’s nature. Hence, non-Muslims are not compelled to convert to Islam (2:256), and they are free to keep their religion. In Surah An’am, Prophet Muhammad (PBUH & HP) is told that: “Had Allah wished, they would not have ascribed partners [to Him]. We have not made you a caretaker for them, nor is it your duty to watch over them.” (6:107). Based on these verses, along with some others, Islam recognizes other Abrahamic religions, and no Muslim is permitted to force any non-Muslim to accept Islamic ideas. Still, Muslims should let non-Muslims to retain their own religious views and beliefs and to live peacefully in society.

3. Peaceful Religious Discussion with Others

If Muslims want to discuss their religious viewpoints with followers of other religions, they are told: “not to argue with the People of the Book, except in a manner which is best” (29:46). It means to exchange peacefully with logical reasoning and argument. Even in their discussions with polytheists, Muslims are prevented from insulting those whom they invoke besides Allah Almighty; otherwise, they would affront Allah Almighty out of hostility (6:108) [1]. It should be noted that the aim of these discussions should be clarifying the truth and not obliging others to convert. As stated above, no one is forced to accept what we believe. This manner ensures Muslims and non-Muslims peaceful coexistence in the Quran.  

4. Islam recognizes other religions

In surah Baqara, it is stated that Prophet Muhammad (PBUH & HP) and the faithful have faith in what has been sent down to him (PBUH & HP) from Allah Almighty, and they believe in Allah Almighty, His angels, His scriptures and His apostles, and they make no distinction between any of His apostles (2:285). It means that a real believer should recognize all previous Prophets sent by Allah Almighty and what they have brought to humans from Him [2]. Besides, in Ayat 62, the followers of other religions like the Jews, the Christians, and the Sabaeans who are faithful to Allah and the Day of Judgement and act righteously are told to have their reward from Allah Almighty (2:62). This is another proof that Islam recognizes other religions. Also, it reveals that there have been faithful people among the followers of other religions who truly believed in Allah almighty according to the teachings of their faith.

5. Islam Encourages Peace-Making

In dealing with the opponents of Islam, Islam orders Muslims to accept if they offer peace and declare a ceasefire and emphasizes that: “Allah does not allow you any course [of action] against them” (4:90). In other verses, Muslims are told that: “If they incline toward peace, then you [too] incline toward it” (8:61). 

6. Marriage and Friendship with non-Muslims

Another example that demonstrates Islamic teachings promote peaceful coexistence in the Quran with non-Muslims is that in the Quran, Muslims are told that: “the food of those who were given the Book is lawful to you, and your food is lawful to them” (5:5). Besides, according to the Quran, Muslim men can marry the chaste ones from among faithful women, and chaste women of those who were given the Book before Muslims, once their dowries are paid to them (5:5). These two instances show that Muslims are free to fraternize with non-Muslims and exchange with them in society.

What has been mentioned above are only some of the many Islamic guidelines that encourage treating others kindly and behaving friendly with the followers of other religions. That makes them incline slightly towards Islam, such that after a Christian boy who had converted to Islam changed his bad behavior with his mother, the mother was attracted and converted to Islam, too. This, together with many instances of the way that Prophet Muhammad (PBUH & HP) and Infallible Imams (AS) treated non-Muslims, proves Islam's deep care for the way Muslims deal with others which should ultimately lead them toward tolerance and maintaining a peaceful coexistence as stated in the Quran.  

References:

1.  M. A. Amini, “The principle of peaceful coexistence with non-Muslims in Islam,” Ma’rifat Journal, no. 165, p. 35-52.
2.  M. H. Tabataba’ei, “Translation of Tafsir Al-Mizan, “vol. 2, p. 681.