What is the religiously sanctioned mourning for the deceased's relatives and its duration? Thank you.

It is not permissible for any of the deceased's relatives to mourn for more than three days, except for the wife, who mourns for her deceased husband for four months and ten days. This is based on the Almighty's saying: "And those of you who die and leave wives behind them, they shall wait concerning themselves for four months and ten days" [Al-Baqarah: 234], and on the Prophet's (PBUH) saying: "A woman should not mourn for a deceased person for more than three [days], except for her husband, for four months and ten [days]."