Bava Metzia 61 - 7th Day of Pesach - April 29, 21 Nissan

What is the source indicating that both the borrower and lender are prohibited from borrowing or lending on interest? Why did the Torah find it necessary to delineate separate negative commandments for interest, theft, and exploitation (ona'ah), rather than deriving one from the other, considering their similarities in taking what isn't rightfully theirs? Furthermore, why does the Torah mention the Exodus from Egypt in verses concerning interest, tzitzit, and using fair measurements in business? Rabbi Yochanan and Rabbi Elazar debate whether the court can compel individuals who have collected interest at a fixed rate from the outset (ribit k'tzutza) to return the interest payments they received.