And you shall eat before Hashem your God, in the place that He will choose to make His Name dwell there, the tithe of your grain, of your wine and of your oil, and the firstborn of your herd and of your flock, in order that you may learn to fear Hashem your God all the days.
English: "And you shall eat" — "You shall surely tithe ... and you shall eat" — and not one who sells.
On the daf / in context: The biblical obligation to separate ma’aser applies primarily to one who finishes the produce in order to eat it himself; one who finishes it in order to sell it is exempt from the Torah obligation (though rabbinically obligated).
Type of Learning
Derash on the verse (Bava Metzia) — the seller is exempt from biblical ma’aser.
What Is Learned
One who processes produce for sale is exempt from the biblical obligation of ma’aser; only one who processes it for his own consumption is obligated by Torah law.