Sefer HaChinuch ספר החינוך

That we not demand the debt of a poor person that does not have with what to pay: That we have been prevented from demanding the debt of the borrower at the time that we know that he cannot pay his debt, since he does not have [the money] — as it is stated (Exodus 22:24), “do not be to him as a creditor.” And know that this preventing also includes not to lend with interest to [another Jew].

It is from the roots of the commandment [that it is] to fix within us the trait of kindness and pity. And when they are fixed within us, we will then be fit to receive the good, and God will fulfill His will through us, as He desires [to do good] in this world and in the next world.

From the laws of the commandment is that which they, may their memory be blessed, said (Bava Metzia 45b), “From where [do we know] about one who gave a hundred to his fellow and knows that he does not have it, that it is forbidden to pass in front of him (across from his home)? As it is stated, ‘do not be to him as a creditor’”; and that which they also said in Mekhilta DeRabbi Yishmael 22:24:4, “do not be to him as a creditor” — that he should not see him all the time. And other things are said about this matter in [Bava] Metzia and in [various] places in the Gemara. (See Tur, Choshen Mishpat 97.)

And [it] is practiced by males and females in every place and at all times. And one who transgresses it and demands his loan [back] from his fellow and knows that he does not have it, but demands it [regardless] in order to cause him pain, has violated this negative commandment and it is as if he has violated the commandment of the King.