Is the reading of Yasin khatam in Masjid after someone dies a sunnah or a custom?

Almighty Allah Taãla states in the Noble Qurãn, 'O` you who believe!! Obey Allah and His Rasul'.

The life of the Prophet (Sallallaahu Álayhi Wasallam) is indeed the best example for us to follow. During the time of the Prophet (Sallallaahu Álayhi Wasallam) many of his family members, his wives, daughters, uncles and his illustrious companions left the world whilst engaged in the most noble work and effort of uplifting the religion of Islam. Despite the Prophet's deep love for them, he did not (on any single occasion) commemorate the innovative custom of 7 days, 40 days, 100 days, etc.

The Hadith is clear, in that, the immediate family should mourn for three days. There is no basis in the Shariáh to commemorate any Muslim's death at intervals of 7 days, etc.

It is not exactly clear as to the source of celebrating forty days after death. We, as Muslims, follow the Noble Qurãn and the life model of our beloved Rasul (Sallallaahu Álayhi Wasallam).

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai