פירוש על חלה 3:6

ספק חייב – because there is a doubt about a prohibition, and we follow the stricter practice, so we separate the Hallah and sell it to a Kohen.

A convert who converted and had dough: if it was made before he became a convert, he is exempt [from hallah]. After he converted, he is liable. As we learned in yesterday’s mishnah, a non-Jew’s dough is not subject to hallah. If a non-Jew has dough, and then converts, the dough is not subject to hallah if he made it before he converted. If he made it after he converted, it is subject to hallah.

ואין חייבין עליה חומש – a foreigner (i.e., non-Kohen) who eats it does not pay the additional one-fifth, but he pays the principal. The payments of Terumah are an atonement. Therefore, we separate the payments and atone out of doubt, and sell them to the Kohen.

And if there is doubt, he is liable, but [a non-priest who has unwittingly eaten of such hallah] is not liable for the additional one-fifth. If it is unclear whether he made it before he converted or not, then he must give hallah. However, this hallah is not treated as “certain” hallah, rather just as “doubtful” hallah, meaning it may or not be hallah. It should be eaten by a priest but if a non-priest eats it, he must restore to the priests the value of that which he ate, but not an added fifth. Only one who eats “certain” hallah must pay back an added fifth of the value, which is the same law that governs terumah.

אחר הקרימה בתנור – for Rabbi Akiba holds that completion of work [to make it liable] for Hallah does not occur until the formation of a light crust on the face of the dough in the oven. And this is the stage for Hallah. Therefore, if he converted prior to the formation of a light crust on the face of the dough in the oven, he is liable for Hallah. But the Halakha is not according to Rabbi Akiba.

Rabbi Akiva said: it all depends on the [time of the] formation of the light crust in the oven. In all of the above mishnayot we learned that dough becomes liable for hallah once it is rolled. Rabbi Akiva disagrees with all of these mishnayot and holds that the end of processing for dough, meaning the point at which it becomes obligated for hallah, is when it forms a light crust in the oven. This is derived from Numbers 15:19 which reads, “And it will be when you eat from the bread of the land, you shall take out terumah for the Lord.” The operative word here is “bread” once it can be considered bread, then one must remove hallah.