Bismillah

Al-jawab billahi at-taufeeq (the answer with Allah's guidance)



There are no reports from the Prophet (Sallallahu Alaihi Wasallam), Sahabah and the Tabi'een (successors) regarding this practice. Therefore, Du'a after Salatul Janazah is Bid'ah and not permissible. (Ahsanul Fatawa Vol. 1 Pg. 336)

(Also see: Fataawa Sirajiyyah Vol.1 Pg.141, Mirqat Sharh Mishkat Vol.2 Pg.319, Mazahirul Haq Vol.6 Pg.57, Khulasatul Fataawa Vol.1 Pg.225)



And Only Allah Ta'ala Knows Best.