Is it permissible to stay overnight with one's sick and blind father during the 'iddah period, in order to relieve the burden on the siblings, without leaving his house except to return to the marital home?

A woman observing the 'iddah (waiting period) after her husband's death is not permitted to spend the night outside her home, except in cases of necessity. We do not see a compelling necessity here, as long as there is someone to care for your father. You are permitted to go out during the day to care for him.