פירוש על ברכות 43:25

I.e. useless, because in view of this teaching it will very rarely be required, the presumption being that the Ba'al Keri is responsible for what happened.

The modern el-Uz, a town in Upper Galilee where the Sanhedrin removed from Jabneh after the death of Rabban Gamaliel. It was the locale of a famous academy.