The prohibition of taking dogs as pet.

 The prohibition of taking dogs as pet. 

Alhamdulillah, it is forbidden in Islam to take dogs as pet. 

But one can take them as for hunting animals and protecting the farm. 

Allah says, 

Al-Ma'idah 5:4

They ask you, [O Muḥammad], what has been made lawful for them. Say, "Lawful for you are [all] good foods and [game caught by] what you have trained of hunting animals[1] which you train as Allāh has taught you. So eat of what they catch for you, and mention the name of Allāh upon it, and fear Allāh." Indeed, Allāh is swift in account.

If one trains the dog, one can use it for hunting but before releasing the animal should mention the name of Allah before releasing it. 

As reported in Hadith, 

Abu Tha'laba al-Khushani reported:

I came to Allah's Messenger (ﷺ) and said: Allah's Messenger, we are in the land of the People of the Book, (so) we eat in their utensils, and (live) in a hunting region. where I hunt with, the help of my bow, and hunt with my trained dog, or with my dog whichis not trained. So inform me what is lawful (Halal) for us out of that. He (the Holy Prophet) said: Regarding what you have mentioned of the fact that you live in the land belonging to the People of the Book and so you eat in their utensils, but if you can get utensils other than theirs, then don't eat in them; but if you do not find any, then wash them and eat in them. And regarding what you have mentioned about (your living) in a hunting region, what you hunt, (strike) with the help of your bow, recite the name of Allah (while shooting an arrow) and then eat; and what you catch with the help of your trained dog, recite the name of Allah (while letting oil) the dog and then eat it, and what you get with the help of your untrained dog, (if you find it alive) and slaughter it (according to the law of the Shari'ah), eat it.

Sahih Muslim 1930.

If one keeps a dog without any reason, each day a qira'at is remove from his good deeds each day.. 

Narrated Abu Huraira:

Allah's Messenger (ﷺ) said, "Whoever keeps a dog, one Qirat of the reward of his good deeds is deducteddaily, unless the dog is used for guarding a farm or cattle." Abu Huraira (in another narration) said from the Prophet, "unless it is used for guarding sheep or farms, or for hunting." Narrated Abu Hazim from Abu Huraira: The Prophet (ﷺ) said, "A dog for guarding cattle or for hunting."

Sahih al-Bukhari 2322.