Then you shall declare in the presence of the LORD your God, “I have removed from my house the sacred portion and have given it to the Levite, the foreigner, the fatherless, and the widow, according to all the commandments You have given me. I have not transgressed or forgotten Your commandments.
Concerning the disposal of their tithe the third year we had the law before, Deu 14:28, Deu 14:29. The second tithe, which in the other two years was to be spent in extraordinaries at the feasts, was to be spent the third year at home, in entertaining the poor.
Commenting on Deuteronomy 26:12-15
Then thou shalt say before the Lord thy God,.... Make the following declaration as in his presence; for this was not made in the tabernacle or temple at, Jerusalem, since the tithe was to be eaten with the poor in the gates of the owner, as in Deu 26:12, I have brought away the hallowed things out of mine house: which Aben Ezra and Onkelos...
thou shalt say before the Lord thy God, I have brought away the hallowed things out of mine house--This was a solemn declaration that nothing which should be devoted to the divine service had been secretly reserved for personal use.