Ketuvot 23 - 29
“A non-kohen who says birkat kohanim (“the priestly blessing”) is transgressing a positive Torah mitzvah.”
Rashi explains that this is learned from the verse (Num. 6:22-27), “This is how you (kohanim) will bless the Jewish People...” The intent is that this beracha is a mitzvah only for a kohen to say, but is forbidden for a non-kohen to say. (See Shulchan Aruch Orach Chaim 128:1 where the Rema cites this prohibition.)
However, the widespread custom is that even a non-kohen says this beracha on occasion, such as when parents bless their children on Friday night and prior to Yom Kippur. The Chafetz Chaim in his commentary Bi’ur Halacha records that it was the custom to bless a person setting out to travel with birkat kohanim and asks how this could be permitted. He insists that since it was a widespread custom it must be permitted. He reasons that it is permitted since the one saying this beracha is not fulfilling the Torah mitzvah of birkat kohanim and therefore he is not transgressing. And although he may not have had explicit intent not to fulfill the mitzvah, it is considered as if he had intent not to fulfill the mitzvah since he is saying birkat kohanim not as part of a prayer service.
- Ketuvot 24b
“These people believed to testify when they become adults about what they saw as minors… a certain person went from school to the mikveh to be able to eat teruma at night…”
The gemara on this mishna explains that this statement in our mishna refers to testimony that would permit eating food that is teruma according to rabbinical law (such as apples and oranges), but not food that is teruma by Torah law (such as grapes, grains, or olives). The inference from this mishna is that a person may testify only when he becomes an adult even regarding a matter of rabbinical law — teruma d’rabbanan — but may not testify while he is still a minor.
Tosefot poses an apparent contradiction. Why is a minor’s testimony not accepted to permit a person to be considered a kohen for the purpose of eating teruma d’rabbanan, whereas we learn in the gemara in Pesachim (4b) that a minor is indeed believed to testify that a house has been checked for chametz, also a mitzvah d’rabbanan?
The difference, explains Tosefot, is that checking for chametz (“bedikat chametz”) is something that is within the power of the minor to do and accomplish. Therefore the Rabbis who instituted the requirement to check for chametz also determined that a minor has the credibility to testify that it was done. Other commentaries explain that he is believed to testify only if he says that he actually did the bedikat chametz. Another approach is that bedikat chametz is something that is done yearly in every home, and every person — including a minor — has great awareness of what is involved. Accordingly, even a minor is careful and serious about the matter and is therefore believed.
- Ketuvot 28a