Why is it impermissible to keep a dog at home as a pet, and why is its saliva considered impure, given the presence of Hadith stating that keeping a dog at home removes blessings and that it is forbidden to keep one except for hunting?

The Sharia permits owning dogs for specific purposes, such as hunting, guarding livestock, and crops. This can be extended to what is more important or similar, like guarding homes and detecting drugs. Anything other than that exposes its owner to a daily decrease in reward. The underlying reason is the existence of a benefit; if a benefit exists, then owning is permissible. So, if the house is in the middle of the city, there is no need to acquire a dog for guarding. However, if it is in a remote area, it is permissible. The Sharia has commanded the spilling of water from a vessel licked by a dog due to the impurity of its saliva. Modern medicine has proven the existence of multiple harms, and a Muslim obeys the Sharia command whether they know the wisdom behind it or not.