Reference for Bava Metzia 29:17

א"ל רב חייא בר אבין לרבא אלא מעתה מתנה דלא כתיב ליה הכי ה"נ דלא טריף שבחא א"ל אין

[But] Abaye said to him: Is it permitted to borrow a measure [of corn and to repay the loan] with [the same] measure, when there was a formal act of acquisition [whereby the borrower pledged himself to be immediately responsible to the lender for an increase in price]? — He [R. Joseph] answered him: There [it is] a loan; here [it is] a sale.

Jastrow