Or HaChaim on Deuteronomy 24:17/אור החיים על דברים כ״ד:י״ז

1 לא תטה משפט גר יתום, "You must not pervert the judgment of a proselyte or an orphan, etc." You might be inclined to favour the proselyte in judgment seeing the Torah has commanded us so many times to love the proselyte. The Torah therefore saw fit to warn us not to pervert his judgment even in his favour. The Torah continues by writing: "do not take the garment of a widow as a pledge," in order to demonstrate that this is the only exception when the Torah does treat a widow differently in judgment compared to ordinary people. You must not take this pledge after the loan has been extended though you may take the garment as collateral at the time the loan is extended.