Yalkut Shimoni on Torah 474:9

"And the priest shall make atonement for him concerning his sin which he has sinned in one of these, and he shall be forgiven" (Leviticus 5:13). What does Scripture teach? For one might think that the more severe among them should be atoned with a lamb or a goat, and the lighter among them with a bird, and the lightest of the light among them with a tenth of an ephah; Scripture states "in one of these," to equate the light ones with the severe ones for the lamb and female goat, and the severe ones with the light ones for the tenth of an ephah.