What is the extent of the validity of a sleeping person seeing the deceased in a dream, and is it considered a reality or a jumble of dreams?

It is not within our specialization to interpret dreams, but we will guide you on how to deal with what a person sees in their sleep: If one of you sees a dream that he likes, then it is from Allah, so let him praise Allah for it and speak of it. And if he sees something else that he dislikes, then it is from Satan, so let him seek refuge from its evil and not mention it to anyone, for it will not harm him. And if one of you dreams a frightening dream, let him spit to his left and seek refuge in Allah from its evil, for it will not harm him.