Yoma 49 - A mistake of Rav Sheshet

They asked Rav Sheshet a question, "If a Kohen carries a part of a sacrifice in his left hand, is it valid or not?" He replied, "We should learn the answer from Yom Kippur: the High Priest carries the incense in his left hand, and the coals in his right, and that is OK!" Firstly, why does he have to bring such strong proof from Yom Kippur? - Because he wants to show that even in this serious case where atonement depends upon it, the service done with the left hand is still valid. But secondly, we learned an explicit ruling that any service done by a blemished Kohen while sitting or with the left hand is invalid! With this, Rav Sheshet's answer is completely disproved.

And Rav Sheshet, how could he make such a mistake? We have heard him quote this explicit ruling in another situation!? The answer is exactly that: previously, he did not know this ruling, so he compared it to Yom Kippur, then they taught him this ruling; now he changed his mind, and in fact, later taught it to others.

Another question: if a High Priest scooped the incense but died before he got a chance to bring it to the Holy of Holies, can a substitute High Priest use his prior scooping, or does the procedure have to be repeated? Here, after a few attempts, the Talmud does arrive at the answer: since later on the High Priest will have to pour the incense out into the shovel and then scoop from it again, we see that a substitute High Priest can do the same in case the first one dies. This proves it.

Art: Study Of Clasped Hands By Andrea Boscoli