“…Allah fashioned the human, as well as every type of creature, to naturally interact with similar creatures. The closer these two creatures are, the more they will interact and become similar to each other in their manners and characteristics, to the point that one would be unable to distinguish between them except in terms of their physical appearance.
Since human beings are closest to each other, their interaction with and imitation of each other is the strongest. Although not as strong, the closeness of humans to animals is intermediate, and there must be interaction and imitation between them to a certain degree as well. Although extremely weak, there is also a degree of closeness between humans and plants, and there must also be interaction and imitation between them to a certain degree.
Due to this principle, human beings are affected by each other in obtaining certain manners and characteristics as the result of being close to and living with each other. So, if a human lives amongst a certain type of animal, he will eventually obtain some of that animal’s characteristics. This is why boastfulness is a characteristic of camel-herders, tranquillity is a characteristic of sheep-herders, and those who raise mules eventually develop some repugnant characteristics of mules, and this is also the case with those who raise dogs. The same applies for animals that spend much of their time around humans: you will find that they obtain some of the characteristics of humans due their constantly being around them.
So, external closeness between creatures gradually and silently leads to internal closeness between them. I have seen how the Jews and Christians who live amongst the Muslims are not as severe in their kufr as those who don’t live amongst them. Likewise, the Muslims who live amongst the Jews and Christians are generally weaker in their faith than the Muslims who don’t…”
[‘Iqitida’ as-Sirat al-Mustaqim ibn Taymiyah’; 1/220]