Forty is a sacred number in Islam , and commemorating the dead forty days after their death is a long-standing Islamic tradition , dating back to the early Islamic period. On the one hand, the fortyth (arba’in, chehellom) signifies the maturation of the soul of a deceased believer. It is thus said that Cain learned on the fortyth birthday of Abel to dispose of his body by burying him, that the ascension of Jesus took place on his fortyth birthday, and that the gates of heaven open for a righteous person forty days after their death.