Charles Ellicott Commentary Deuteronomy 14:23

"And thou shalt eat before Jehovah thy God, in the place which he shall choose, to cause his name to dwell there, the tithe of thy grain, of thy new wine, and of thine oil, and the firstlings of thy herd and of thy flock; that thou mayest learn to fear Jehovah thy God always." — Deuteronomy 14:23 (ASV)

And you shall eat before the Lord your God —that is, you shall eat the second tithe. This was to be done two years; but in the third and sixth years, there was a different arrangement . In the seventh year, which was Sabbatical, there would probably be no tithe, for there was to be no harvest. The profit of the earth was for all, and everyone was free to eat as they pleased.