How authentic is the Hadith that mentions a man named Mujashshir coming to the Messenger of Allah (peace be upon him and his family) and asking him about the path to knowing the Truth, and its approval, satisfaction, connection, obedience, remembrance, proximity, and intimacy, with the Messenger's answer each time being about dealing with the self?

It appears that the aforementioned hadith (definition) is fabricated and has no basis in the authentic books of hadith. It has been found in the references of innovators with an unlinked chain of transmission. The scholars of hadith terminology have stated that the worst fabricators are those who sought reward by fabricating hadith to encourage people to do good. Among the signs of a fabricated hadith is the weakness of its style, and this hadith contains phrases that raise jurisprudential and linguistic concerns, such as "alienation from the self" and "abandoning the self."