Deuteronomy 24:15

In his day thou shalt pay him his hire. Nor let the sun go down upon it; because he is poor, and he hopes (for that hire) to sustain his life: lest he appeal against thee before the Lord, and it be guilt in thee.

on the same day you will pay him his wage — the sun shall not set Scripture adds on a negative commandment, for emphasis,

with it i.e., with his wage,

he supports himself the reason he hires himself out is in order to sustain himself therefrom.

IN THE SAME DAY THOU SHALT GIVE HIM HIS HIRE, NEITHER SHALT THE SUN GO DOWN UPON IT. The meaning thereof by way of the plain sense of Scripture is that this explains what is stated in the Torah, the wages of a hired servant shall not abide with thee all night until the morning, for it is the manner of verses to speak of the common occurrence, and the custom is to hire a laborer for one day and for him to leave toward evening before sunset. And so Scripture commands [the employer] to pay him during his day as soon as he finishes his work, and that the sun should not set upon him [before he is paid], in order that he should be able to purchase with his wages what he, his wife, and his children, need to eat at night, for he is poor as are most of those who hire themselves out for the day, he has staked his life upon this wage to buy with it food to sustain his life. Thus he teaches us here that the intent of what He said in the Torah, the wages of a hired servant shall not abide with thee all night until the morning is that you pay him during his day, for if you do not pay him when he leaves his work, he will go home and his wage will be left with you until morning and he may die of hunger at night. In a similar way is the verse, for that is his only covering, it is his garment for his skin; wherein shall he sleep? It states the reason for the commandment in most of these prohibitions. And our Rabbis have explained that the verse [the wages of a hired servant shall not abide with thee all night] until the morning applies to a day-worker [who departs from work at sundown; the time for paying him his wages is the entire night, and this law is not violated before daybreak]. Then he reverted to explain here the law of a man who is hired for night-work [whose departure from work is at daybreak and the time for paying his wages is the whole day and the law is not violated until sundown]. Thus for each one, there is a twelve hour deadline for payment. This is the truth as received by tradition and is appropriate with correct interpretation.

ואליו הוא נושא את נפשו, for his very soul is in dire need of it (so that he can buy food to sustain himself). He had put himself at risk working (instead of begging) in order to receive his wages. We find a verse with a similar message in Hoseah 4,8 חטאת עמי יאכלו ואל עונם ישאו (נפשם). “The priests are dependent on the meat from the sin offerings, so that they actually hope for the people to sin so that they will be provided with such meat by being instrumental in obtaining expiation for the sinners.”