Reference for Pesachim 2:2
חָמֵץ שֶׁל נָכְרִי שֶׁעָבַר עָלָיו הַפֶּסַח, מֻתָּר בַּהֲנָאָה. וְשֶׁל יִשְׂרָאֵל, אָסוּר בַּהֲנָאָה. שֶׁנֶּאֱמַר (שמות יג) לֹא יֵרָאֶה לְךָ שְׂאֹר:
It is permitted to derive benefit from the chametz of a gentile over which Pesach has passed. [This is not to say that it is forbidden to eat it — but since it is to be taught: "and it is forbidden to derive benefit from that of an Israelite," the antithesis is stated in respect to a gentile. Or else, because there are some who forbid to themselves the bread of a gentile, it is not stated explicitly: "It is permitted to eat the chametz of a gentile."]; and it is forbidden to derive benefit from that of an Israelite, it being written (Exodus 13:7): "Se'or (leaven) shall not be seen unto you." [That is, he is penalized for having transgressed "Se'or shall not be seen unto you." Or else, this refers to the beginning, viz.: "The chametz of a gentile is permitted," it being written: "Se'or shall not be seen unto you," which is expounded: What is yours, you may not see, but you may see what is a gentile's.]