Deuteronomy 24:3

And [if] the latter husband hate her
Or less loves her than another woman, and she is disliked by him as she was by her former husband;

and write her a bill off divorcement, and giveth [it] into her hand,
and sendeth her out of his house:
as he had by this law a permission, in like manner as her former husband had; (See Gill on Deuteronomy 24:1);

or if her latter husband die, which took her [to be] his wife;
and she survives him; as she is then by death loosed from the law of an husband, she may lawfully marry another man, but not her former husband, as follows.