Ramban on Deuteronomy 24:15

The reason you must give the worker his wages during the day and not let the sun set on them: According to the plain meaning of the text, this rule is clear from what is written elsewhere (Leviticus 19:13)--do not keep the wages of a hired laborer with you until the morning. It is the way of the text to address the common situation, and it is the custom to hire workers for one day, and in the evening they leave before sunset. And the verse commands payment on that day, as soon as the worker has finished the work, before the sun sets, so that he may use his wages to for himself, his wife, and his children something to eat that night. “For he is poor”--like the majority of hired laborers, and he depends on the wages to buy food by which to live. This teaches that when the Torah says, “do not keep his wages with you until morning,” the intention is that he should collect the wages on the day he works, for if he does not collect the wages right away as he is leaving work, he will go home, and his wages will remain with you until the morning, and he will die of hunger that night. [Translation by Rabbi Jill Jacobs]