John Chrysostom — as excerpted in the Catena Aurea on Matthew 22:23-33

“(non occ.) For because death to the Jews, who did all things for the present life, seemed an unmixed evil, Moses ordered that the wife of one who died without sons should be given to his brother, that a son might be born to the dead man by his brother, and his name should not perish, which was some alleviation of death. And none other but a brother or relation was commanded to take the wife of the dead; otherwise the child born would not have been considered the son of the dead; and also because a stranger could have no concern in establishing the house of him that was dead, as a brother whose kindred obliged him thereto.”