What is the ruling on this oath sworn by a cannabis addict, that he will be eternally in Hell and that no prayer, fasting, or any act of worship will be accepted from him if he returns to it, and will his repentance be accepted after he has returned to it several times, and what must he do for abandoning prayer due to a guilty conscience?

A person's supplication against themselves out of fear of falling into sin is not permissible. Any supplication or oath mentioned does not constitute a legal oath (yamin shar'iyyah), nor does it necessitate expiation (kaffarah). Drinking hashish and other intoxicants is a grave sin (kabirah min kaba'ir adh-dhunub). Abandoning prayer is an abominable disobedience. Whoever abandons it while denying its obligation is a disbeliever (kafir). Abandoning it out of laziness is a great danger. One must hasten to repentance and make up all missed prayers to the best of their ability. The idea that Allah does not accept prayer is one of Satan's stratagems. Allah accepts repentance and rejoices in it. The door to repentance is open as long as the soul has not reached the throat. Therefore, one must hasten before the appointed time passes.