Rabanus Maurus — as excerpted in the Catena Aurea on Matthew 3:11-12

“There is this difference between the chaff and the tares, that the chaff is produced of the same seed as the wheat, but the tares from one of another kind. The chaff therefore are those who enjoy the sacraments of the faith, but are not solid; the tares are those who in profession as well as in works are separated from the lot of the good.”