Questions about Islamic Veil (Pardah) and a Historical/Religious Incident

The Devar (husband's younger brother) and Jeth (husband's elder brother) are both non-mahram (strangers in terms of marriage) to a woman; therefore, observing the Shar'i Pardah (Islamic veil/modesty) is obligatory (Fardh/Laazim) with respect to them. This Pardah is also necessary inside the four walls of the house. Your understanding that marriage is permissible with them after the husband's death is absolutely correct, and this is precisely the reason they are considered non-mahram. The Prophet Muhammad (peace be upon him) likened improper interaction (lack of pardah) with the Devar (and Jeth) to "death", as the risk of moral and religious corruption is significantly higher with them. Therefore, greater caution is required with them than with a typical unrelated man. No, the incident of Prophet Musa (Moses), peace be upon him, is that the Angel [of Death] came to him. Prophet Musa became angry because he felt he still had work left to do for the Deen (religion). That is why, upon the Angel's statement (that his time had come), he slapped the Angel of Death. The Angel went to Allah and said, 'He did this to me.' Then the Angel returned and clarified to Prophet Musa that death is inevitable. Upon this (realization), he said, 'Then take my soul now.'