Rambam, Mishneh Torah, Laws of Lending and Borrowing 1:1

It is a positive mitzvah to lend to the poor, as it is said, “You should lend money to my poor, the poor of your people.” One might have thought this was a discretionary act. But the Torah teaches, “You must open your hand and lend him sufficient for whatever he needs” (Deuteronomy 15:8). And this mitzvah is greater than [giving] tzedakah to the poor who ask for it, for he is already at the stage where he must ask, while this one has not yet reached that stage. And the Torah specifically rebukes one who refrains from loaning [to the poor in this manner], as it is said, “[If] you are mean to your kinsman and give him nothing, he will cry out to God against you, and you will incur guilt.” (Deuteronomy 15:9). [AJWS translation]