Listening to the instructions and will of one’s parents after death:
A son or daughter is obligated to listen to the instructions of their parents even after their death. Thus, one must listen to one’s parents will. This applies even regarding those monetary matters that are found in the will which are contrary to the monetary laws of inheritance, nonetheless, one must obey his parents will of distribution due to the mitzvah of Kibbud Av Vaeim. However, one is not obligated to listen to the will of his parents regarding making monetary payments from monies that he did not inherit from them.
Mother asked son not to rent his home to any individual after her death: If one’s mother or father instructed him not to rent his house to anyone, then he may not do so even if the person who desires to rent the home is a Torah scholar who will learn Torah in a group for the benefit of the soul of the deceased parent.
Father instructs son to write shameful matters on the tombstone: If a father instructs his son to write shameful matters on the tombstone, then the son is not allowed to listen to him.
 Haradbaz 3:535; Maharsham Y.D. 95; Tashbeitz 2:53; Shut Rav Akiva Eiger Kama 68; Mahariy Asad 2:44; Maharsham 2:224-16; Minchas Elazar 2:63; Chazon Nachum 118; Pesakim Uteshuvos 240:32; See regarding the mitzvah to listen to the will of any person who has passed away even if it is not his parent: Admur C.M. Mechira Halacha 7; Michaber C.M. 252; 250:23; Smeh 252:8; Shach 252:4, 7; Nesivos Hamishpat 256:2; See Encyclopedia Talmudit ibid P. 462 Footnotes 1206-1213
Other Opinions: Some Poskim rule that a child is not obligated to listen to his parents’ instructions after their passing. [Shvus Yaakov 1:168; See Rav Akiva Eiger ibid; Encyclopedia Talmudit ibid footnote 1212-1213]
 In certain cases, the instructions in the will which ran contrary to the Jewish law of inheritance are considered Halachically binding and overrule or circumvent the Jewish laws of inheritance. This would include the following cases: 1) The parent was considered a Shechiv Meira, fatally ill, at the time that the instructions were given or written in which case we consider the distribution to having took place before the death. [Michaber C.M. 250; See also Beis Yosef C.M. 250:15; Maharsham 2:224-16] 2) A premortem gifting document was signed by the parent in which it is written that the assets became distributed a moment that before death. 3) A Shtar Chatzi Zachar IOU document was signed.
 The reason: Although one is not required to honor his parents with his own money, and hence one can argue that one is not obligated to respect his parents will regarding the money that he legally and Halachically inherited from them, nonetheless, since the money originally belonged to the parents, and their instructions were given while they still owned the money, their instructions are therefore to be respected. [Maharsham 2:224-16] This is in addition to the mitzvah to listen to the will of any person who has passed away even if it is not his parent. [Michaber C.M. 252; 250:23; Smeh 252:8; Shach 252:4; Nesivos Hamishpat 256:2]
 Chavos Yair 214, brought in Pischeiy Teshuvah 240:23; However, see Kneses Yechezkal 35, Vetzaruch Iyun
 Doveiv Meisharim 1:108; Maharsham Y.D. 203; Minchas Elazar 2:63