Reference for Menachot 141:4
אלא אמר שמואל (דברים טז, ט) מהחל חרמש לאו מכלל דאיכא דלאו בר חרמש דלאו בר חרמש ולעולם שחת
GEMARA. It was taught: R. Benjamin says, The verse says, When ye shall reap the harvest thereof, then shall ye bring the sheaf. and following that it says, The first of your reaping unto the priest. How is it to be explained? Thus, the field from which you may bring [the 'Omer] you may not reap [before the 'Omer]. but that field from which you may not bring [the 'Omer] you may reap [before the 'Omer]. Perhaps I ought to say this: that kind of grain from which you may bring [the 'Omer] you may not reap [before the 'Omer], but that kind from which you may not bring [the 'Omer] you may reap [before the 'Omer]! - You cannot say so on account of R. Johanan's teaching. <br>