Deuteronomy 24:2

And when she is departed out of his house
With her bill of divorce, by which departure out of his house it is notified to all:

she may go and be other man's [wife];
it was permitted her to marry another man, she being by her divorce freed from the law of her former husband; and who indeed, in express words contained in the divorce, gave her leave so to do; which ran thus,

``thou art in thine own hand, and hast power over thyself to go and marry any other man whom thou pleasest; and let no man hinder thee in my name, from this day forward and for ever; and, lo, thou art free to any man;''

(See Gill on Matthew 5:31).