+ Positive Mitzvah
Marry the wife of the deceased brother who has no children. (Yibum)
“If brothers dwell together and one dies and has no children, the wife of the deceased shall be taken as a wife by the husband’s brother”. Devarim 25;5
In our times there is no proper intention to perform the Mitzvah to perpetuate the name of the deceased brother.
No law of Yibum/ the levirate marriage is applicable, only removal of the shoe (Chalitza) that follows.