What is the ruling on one who became afraid upon hearing that a certain soothsayer predicted his death on a specific day, believing that a Jinn revealed this to the soothsayer, and not that the soothsayer knows the unseen?

The fear of death is a natural fear. Do not believe the soothsayer in what he tells, because before the prophethood of Prophet Muhammad (peace be upon him), the jinn would eavesdrop from the heavens and convey news to the soothsayers. However, after his prophethood, the heavens were guarded with meteors to prevent the devils from listening, as stated in the Almighty's saying: "And we have sought [to ascend to] the heaven and found it filled with powerful guards and burning flames" (Al-Jinn: 8). This guarding continues after the death of the Prophet (peace be upon him) to prevent the return of soothsaying.