Is it permissible to keep a dog at home to bring joy to a child severely afflicted with autism who loves dogs and is calmed by them, preventing his fits of anger that lead him to break furniture and scream?

It is not permissible to keep a dog except for what the Shari'ah has exempted, such as a dog for hunting, herding, or farming, because keeping it results in a reduction of one or two Qirats from the owner's reward daily, and because angels do not enter a house in which there is a dog, except for dogs permitted to be kept. Jurists have differed on keeping a dog for guarding homes, and the preponderant opinion is that it is permissible if the home needs guarding.