[If] one gathers up peah, and says: “Behold, this is for such and such a poor man” —- R' Eliezer says: He has acquired it for him; but the Sages say: He must give it to the poor man that is met first.  The leket, the shich'chah, and the peah of a non-Jew are liable to tithing, unless he declared [them] ownerless.

Similarly: [If] one consecrated his fruits before they arrived at the tithing stage, and redeemed them, they are liable. [If he consecrated them] after they arrived at the tithing stage, and he redeemed them, they are liable. [If] he consecrated them before they were finished, and the Temple clerk finished them, and after this [the owner] redeemed them, they are exempt, since at the time of their liability they were exempt.