(Mishnah): One may not take security from as widow, whether she is poor or rich, as the pasuk states (Devarim 24, 17), "Do not take the garment of a widow as security''.

One who takes a millstone as security transgresses a negative prohibition and is liable for two vessels, as the pasuk states (ibid, 6), "You shall not take a lower or upper millstone as security''.

Not only is there a prohibition for millstones, but any utensil used for food preparation (may not be taken as security), as the pasuk states (ibid), "as he would be taking his like as security''.

(Gemara) - Beraisa (R. Meir): One may not take security from as widow, whether she is poor or rich, as the pasuk states (ibid, 17), "Do not take the garment of a widow as security''; meaning whether she is poor or rich.

R. Yehudah: If she is poor, one may not take a security at all; if she is rich, one may take a security but not return it to her as coming to bring it to her might give her a bad name (of being visited by a man).