Sforno on Exodus 22:24/ספורנו על שמות כ״ב:כ״ד

1אם כסף תלוה, if this is an Israelite on whom the promise that “there will not be a destitute person among you” has not been fulfilled. (compare Deuteronomy 15,4) The individual in need of a loan is the one who became subject to another promise (threat) written in the Torah in Deuteronomy 15,11 כי לא יחדל אביון, “there will never be a total absence of destitute people, etc.” When such a situation arises the victim will require a loan.