Hadith: Whoever keeps a dog, except a dog for hunting or for guarding livestock, his deeds will be reduced by two Qirāts every day

عَنْ ابنِ عُمَرَ رَضيَ اللهُ عنهما عَنْ رَسُولِ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ:
«مَنِ اقْتَنَى كَلْبًا إِلَّا كَلْبَ ضَارٍ أَوْ مَاشِيَةٍ نَقَصَ مِنْ عَمَلِهِ كُلَّ يَوْمٍ قِيرَاطَانِ»، قَالَ سَالِمٌ: وَكَانَ أَبُو هُرَيْرَةَ يَقُولُ: «أَوْ كَلْبَ حَرْثٍ»، وَكَانَ صَاحِبَ حَرْثٍ.
[صحيح] - [متفق عليه] - [صحيح مسلم: 1574]

Ibn ‘Umar (may Allah be pleased with him and his father) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said:
"Whoever keeps a dog, except a dog for hunting or for guarding livestock, his deeds will be reduced by two Qirāts every day." Sālim said: Abu Hurayrah, who had a farm, used to say: "Or a farm dog."
[Authentic hadith] - [Narrated by Bukhari & Muslim] - [Sahih Muslim - 1574]

Explanation

The Prophet (may Allah's peace and blessings be upon him) warned against keeping dogs except for the purposes of hunting or guarding livestock and crops. Whoever keeps a dog for other reasons will have two Qirāts, which is a specific measure known to Allah Almighty, deducted from the reward of his deeds each day.

Benefits from the Hadith

1. It is not permissible for a Muslim to keep a dog except in the cases that have been excluded.
2. Keeping dogs is prohibited due to the numerous harm and evil consequences associated with it. It is authentically reported from the Prophet (may Allah's peace and blessings be upon him) that angels do not enter a house that contains a dog. Additionally, dogs carry an intense impurity that can only be removed by repeated washing with water and dust.