Reference for Bava Metzia 123:9

מכלל דתנא קמא סבר לאו בני אהדורי נינהו לא מאי קום עשה לקרוע שטרא

An objection was raised: Robbers, and those who lend on usury, even when they have exacted it, must make restitution. Now, how can 'even when they have exacted it' apply to robbers? If it is robbed, it is robbed; and if not, can you call them robbers? But say thus: Robbers; and those meant thereby are those who lend upon usury, even when they have exacted it, must make restitution! — It is a dispute of Tannaim. For it was taught: R. Nehemiah and R. Eliezer b. Jacob exempt the lender and the surety [from punishment],<span class="x" onmousemove="('comment',' The penalty of lashes attached to the injunction against interest. ');">⁷</span>

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