It was narrated from Abū Hurayrah رضي الله عنه that the Prophet ﷺ said: “Whoever keeps a dog, except a dog for herding, hunting or farming, one Qirāt will be deducted from his reward each day.”
● [رواه مسلم ١٥٧٥]
It was narrated that ‘Abdullāh Ibn ‘Umar رضي الله عنهما said: The Messenger of Allāh ﷺ said: “Whoever keeps a dog, except a dog for herding livestock or a dog that is trained for hunting, two Qirāt will be deducted from his reward each day.”
● [رواه البخاري ومسلم]
As for what is a Qirāt, the Prophet ﷺ said: “Like two great mountains.” i.e keeping a dog without necessity will make its owner lose two Qirāt (four mountains) of reward each day, and Allāh’s Aid is sought.
Imām an-Nawawī رحمه الله said: “There is a difference of opinion as to whether it is permissible to keep dogs for purposes other than these three, such as for guarding houses and roads. The most correct view is that it is permissible, by analogy with these three and based on the reason that is to be understood from the hadeeth, which is necessity.”
● [شرح مسلم ١٠٢٣٦]
Sh. Ibn al-‘Uthaymīn رحمه الله said: “Based on this, if a house is in the middle of the city there is no need to keep a dog to guard it, so keeping a dog for this purpose in such situations is haraam and is not permitted, and it detracts one or two Qirāt from a person’s reward every day. They should get rid of this dog and not keep it. But if the house is in the countryside and there is no one else around, then it is permissible to keep a dog to guard the house and the people who are in it; guarding the members of the household is more important than guarding livestock or crops.”
● [مجموع الفتاوى لإبن العثيمين ٤٢٤٦]
As for the saliva of dog being Nājis (impure) Ibn Taymiyyah رحمه الله said there are several opinions:
• Dog is pure including its saliva = Opinion of Imām Mālik
• Dog is impure including its hair = Opinion of Imām ash-Shāfi’ī
• Dog’s hair is pure but saliva is impure = Opinion of Imām Abū Ḥanīfah and Imām Aḥmad
● [مجموع الفتاوى ٢١٥٣٠]
Sh. Ibn al-‘Uthaymīn رحمه الله also said: “With regard to touching this dog, if there is no wetness then it does not make the hand Nājis (impure), but if he touches it and there is any wetness, then this means that the hand becomes Nājis according to the view of many scholars, and the hand must be washed after that seven times, one of which should be with soil (6 times with water and once with soil).”
● [مجموع الفتاوى لإبن باز ٢١٢١٧]