"Although most modern dogs are kept as pets, there are still a tremendous number of ways in which dogs can and do assist humans, and more uses are found for them every year" [1]. This animal is used in many activities such as rescuing, herding, sledding, hunting, guarding, tracking, and Human Remains Detection.There are also war and police dogs, which all indicate the versatility of this animal. But in Islam, there are some restrictions regarding the relationship with this useful creature.The term "impure" (Najis) in Islamic jurisprudence refers to things that are avoided because of the intensity of filth in them, one of which is dogs. The religion of Islam has warned Muslims to keep dogs “as pets” since they are deemed dirty. Now, let’s see why:

The Impurity of Dogs

Unless properly trained, dogs will defecate and urinate where ever they please; they also slobber everywhere, which doctors say is the cause of many diseases and infections.

Even though the level of awareness about the hazards of having a dog has increased among dog owners and necessary precautions about keeping it as a pet have been taken by them, dog bites continue to be a public health problem in the USA [1].

Doctors always warn about diseases we may catch from dogs: “Hookworms and roundworms (Ancylostoma and Ascaris) are common nematodes of dogs. When a human accidentally eats something contaminated with worm eggs from a pet’s stool, the eggs hatch in the intestines and begin migrating throughout that person’s body” [2].

From the viewpoint of Islam, when we speak about the impurity of the dog, we mean its "outward" filth and all its organs including skin, flesh, and hair. So, everything is considered as "impure" in contact with a wet dog or vice versa (a wet thing in contact with a dog). Almost all Muslim scholars do not doubt that dogs are impure animals. There are many narrations (Hadiths) about the impurity of dogs in authentic narration books, including:

“Allah has not created a creature more impure than dogs” [3].
“If your clothes get dampened by a dog, then you must wash them” [4].

The Fidelity of Dogs

Perhaps, one of the reasons for Islam to prohibit Muslims from keeping dogs as pets [3] is due to the high fidelity of these animals. The bond between dogs and their owners has an important impact on family relationships in a way that the dog owner may forget his family members and relatives, adore his/her pet, and neglect God’s worship as well.

It has been reported that “More and more US women are forgoing motherhood and getting their maternal kicks by owning handbag-size canines” [5].

Trained dogs in Islam

There are possibly two reasons for a person to have a dog: affection for the animal or security.

In the first case, the dog will most probably live with you in your house, which is prohibited according to Islamic law.

And in the second one, the case of security, the dog is mostly kept on the periphery of your house or property; like the dogs that are held for hunting, guarding livestock, crops, and for guarding houses, etc. These dogs are called trained dogs (Kalb-e-Moallam) in Islam and the rules regarding them are different from the ones for the other kinds of dogs.

There are exceptions to them, and they are not considered “impure” because of their skills. This fact has been mentioned in the Holy Quran directly: “As for what you have taught hunting dogs [to catch], teaching them out of what Allah has taught you, eat of what they catch for you and mention Allah’s Name over it …” (5:4)

Do Muslims hate dogs?

But do Muslims consider dogs as filthy and useless creatures? No. because these animals are also creatures of God. Similarly, despite its many benefits and its importance for human life, human blood is also regarded as impure in Islamic teachings.

In other words, dogs’ impurity does not deny the existence of their good features such as loyalty or innocence, just as the impurity of human urine, feces, and blood has nothing to do with his/her humanity.

On the other hand, Islam has proposed very detailed rights for all kinds of animals including dogs, which a Muslim must respect and observe. For example, one day when Imam Hussain (AS) saw his servant sharing his food with Imam’s garden guard dog, he highly admired the servant for his kind behavior, rewarded him with 1000 Dinars and even donated the garden to him just for observing the right of a dog [6].

Is that all?

The words mentioned above reveal the Islamic view of dogs. But is that all? Have we successfully and thoroughly looked into it to reach firm ideas about dogs?

To tell you the truth, we are not always able to understand the essence of Islamic rules and guidelines. More importantly, Muslims have learned to fully observe the practices ordained by God because they believe these practices are best for them, just like following the instructions that come with the electronic devices without questioning them.

If God, the Prophet (PBUH&HP), and infallible Imams (AS) prohibit specific practices, it is definitely because they have certain harmful effects on us that may or may not be immediate or measurable.

“…while He has already elaborated for you whatever He has forbidden you, excepting what you may be compelled to [eat in an emergency]? Indeed many mislead [others] by their fancies, without any knowledge. Indeed your Lord knows best the transgressors.” (6:119)

In a nutshell

It is permissible to keep dogs for security purposes in Islam, but you cannot let them inside your house. However, this does not mean we can harm dogs or hate them, Not at all; on the contrary, we should always be compassionate with dogs as much as we should be with any other living kind.

References:

1. Nicolae Sfetcu, About Dogs.
2. keep pets
3. All Creatures Health Care
4. Vasael Alshia, vol. 1, p. 220 Hadith 560, Imam Sadiq (AS)
5. Vasael Alshia, vol. 1, p. 225 Hadith 571, Imam Sadiq (AS)
6. al about pets
7. Mustadrak Alvasayel, vol. 7, p. 192

Love and kindness are two of the main components of Islam. To the extent that Allah regards Prophet Muhammad (PBUH&HP) as kind and benevolent towards people of all nations in the Holy Quran: “We did not send you but as a mercy to all the nations (21:107).” And says that if he had not been gentle to people, they would have surely scattered from around him. (3:159)

Imam Hussain (AS), following in his grandfather’s footsteps, also placed particular emphasis on this prophetic trait and ethic. He was not only gentle and affectionate towards his children, family, and relatives, but also showed great care, compassion, and respect towards others, even his enemies. The whole Fifty-seven years of Imam Hussain (AS)’s life are replete with such exemplary behavior. He did not give up this attitude towards others even in the hardest situations, like when he was at war with his enemies in the desert of Karbala.

Here we will see only a few examples of Imam Hussain’s (AS) love and affection towards others in the last days of his life: 

Imam Hussain (AS)'s Attention to Children:

During the battle, in Karbala, Imam Hussain (AS) would sympathize with his family and children and treated them with love and care whenever possible. 

Imam Hussain (AS)'s Attention and Respect towards His Companions:

At the night before Ashura, Imam Hussain (AS) refers to his relatives and companions as the best ones ever: “It is a fact that I am not aware of any companions more faithful and honest than my companions and any relatives more righteous and kind than my relatives.” Imam Hussain (AS) then permits all his companions to leave him without any restrictions to save their lives, but they don’t accept. On several occasions, such as the morning of Ashura, he addresses them with the most respectful titles like “the nobles.” Also, it is narrated that during the battle, Imam (AS) would be present near his martyred companions himself, and wept and prayed for them one by one, even for the African slave, Jawn.

Imam Hussain (AS)'s Compassion for His Enemy:

Imam Hussain (AS) never used foul language or even one wrong word against his enemy. He would not hesitate to take advantage of any opportunity to stop the violence and invite his enemies to peace. For instance, when Imam Hussain (AS) and his companions came across Hur, and his army, who were supposed to intercept Imam Hussain (AS) outside Kufa, Imam Hussain (AS) quenched their thirst. He, along with his companions, also even gave water to their horses.

Another example of Imam Hussain’s compassion for the enemy is his encounter with Umar ibn Sa’ad and the other commanders of the enemy’s army on the day of Ashura, and his effort to persuade them to stop the war. In fact, Imam (AS) did not want them to commit an unforgivable sin- i.e., killing the innocent Imam (AS) and his companions- that would make them end up in hell.

So, it was only Imam Hussain's (AS) love and mercy towards humankind that touched every one’s heart, even his enemy to the extent that some of whom, like Hur, would surrender to righteousness, accompany Imam Hussain (AS), perform their prayer in congregation behind him, fight against his enemy and finally be martyred along with him. 

This is Imam Hussain’s (AS) lesson of tolerance and benevolence towards all human beings, which is beyond any religion or sect; that if one does not want to follow a particular religion, he/she can at least live a human life [3].

References:

1.  Imams sermon 
2. last night in Karbala
3. Bihar al-Anwar, vol. 45, p. 49