All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
We ask Allaah to have mercy upon your mother, accept her deeds, and make good your condolence. It should be known to the questioner that if her mother died on the tenth night of Thul-Hijjah after having stood at ‘Arafah on the ninth day of Thul-Hijjah, she would be regarded to have stood along with the pilgrims. However, if she died on the ninth night of Thul-Hijjah before standing at ‘Arafah, then she would not be considered, in reality, to have stood at ‘Arafah. Nevertheless, we expect that Allaah would accept Hajj from her and that on the Day of Resurrection, she would be raised up from death reciting Talbiyah, depending on the Hadeeth that reads, “He who intends to do a good deed and could not do it, it will be written by Allaah a full good deed for him.” [Al-Bukhari and Muslim]
To the best of our knowledge, there is no evidence to support the superiority of death on Monday other than the wish of Abu Bakr to die on it as well as the fact that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, died on it. We have no knowledge of the claim that whoever dies on it will be safe from the torment of the grave.
Allaah Knows best.