Why is Terahvi done after death? (मृत्यु के बाद तेरहवी क्यों की जाती है?)

In Hindu religion, mourning is observed for 13 days after death and then on the thirteenth day a Brahmin feast is held so that the soul of the deceased may find peace and a place in the abode of God. This period of thirteen days is known as Terahvi. According to Garuda Purana, if the thirteenth of the deceased is not performed, then his soul keeps wandering in the Pishacha (vampire) Yoni.Religious Significance of Doing Thirteenth in Hinduism
❀ It is described in Garuda Purana that after death the soul of a person who dies stays at his home for 13 days.
❀ It is believed that the soul carefully watches each and every work done by its family members.
❀ Even the spirit disturbs the person who lights the pyre. hurts her. That's why the person who lit the funeral pyre is not left alone even for a moment for 13 days. Also, the person offering the pyre is always kept with the Bhagavad Gita (Benefits of reciting Bhagavad Gita) or pliers made of iron.
❀ It is believed that for 13 days all the necessary rituals related to the rites of the deceased are performed.
❀ On the last day i.e. on the 13th day, a Brahmin feast is organized and Pindadan takes place.
❀ Thirteenth is considered important in Hinduism because only after this the soul leaves the house.
❀ It is only after the thirteenth that the soul gets liberation and attains the abode of God.
❀ Brahmin Bhog is also very important in the thirteenth because all the rituals are done by Brahmins.
❀ In such a situation, if a Brahmin feast is not organized, then the soul of the deceased gets Brahmin debt.
❀ According to Garuda Purana, this does not give salvation to the soul of the deceased and it has to suffer.
❀ Thirteenth is also necessary so that he can get freedom from the sins given by the deceased.
❀ May the soul of the deceased rest in peace and may he not trouble his family members in any way.

Scientific Significance of Doing Thirteenth in Hinduism
❀ There is also a scientific basis behind doing the thirteenth. Thirteenth is done to avoid depression.
❀ In fact, if a person remains depressed for more than 13 days, then he may be in the grip of depression.
❀ Person’s condition becomes such that he slowly drowns badly in the tension that does not come out.
❀ According to a study conducted at the Institute of Mental Health, being depressed for more than 13 days can even cost one's life.

That's why the limit of 13 days in Hindu religion was fixed by our sages to mourn at that time itself.