How is the estate divided for a man who died and has no children or wife, and his deceased heirs who died before him are a brother from the mother's side, a sister from the mother's side, and a sister from the father's side, and he has no living male agnatic relatives (asabah) or sharers (ashab al-furud), and he bequeathed his entire estate to his nephew from his mother's side while in full health and had it witnessed?

If the deceased has no 'asabah (agnate heirs), the dhawu al-arham (relatives by blood, but not 'asabah or اصحاب الفروض - sharers) inherit. The son of the sister is treated like his maternal aunt (his mother's full sister). The children of the brother and sister from the mother's side are treated like the one through whom they are related (their mother or father). The inheritance is distributed among them similarly. As for singling out his nephew for something, this is not permissible unless it is a will, and in that case, there is no will for an heir.