Is a will regarding the washing and burial of a deceased person binding?

A will made by a person during their lifetime, specifying that a certain individual should wash them, lead their funeral prayer, bury them, or that they should be buried in a specific place, is not binding. (see al-Fatāwā al-Hindiyya, 1/163) However, if the relatives of the deceased wish, they may fulfill this will.

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu