פירוש על קידושין 92:4

Hallah, a portion of one’s dough given to a priest, is supposed to be separated from the dough and not from flour. If one separates it as flour, it is not hallah and if he gives it to the priest, the priest must return it. We do not assume that the man knew that he should not separate dough from flour and that he gave it as a gift to the priest. This is a difficulty on Shmuel who said that we do make such an assumption when it comes to kiddushin.