Beyond that, I am just noting a group of interesting things about hands and brachos. Perhaps there is an association among some or all of them, some unifying theme. I haven't found it yet. Maybe you will.
Three Examples of the Hand as Instrument of Bracha
- The Blessing of Children
- Birkas Kohanim
- The Semicha of Yehoshua
Several interesting things.
1. Two Hands or One?
Let me start with a quote from the Risher Rov, who says in his Hadrash V'ha'Iyun as follows:
If Bracha involves putting your hand on the misbareich, what good is Aharon's lifting up of his hands? He wasn't touching anyone. Of course, as Rabbeinu Bachay says, by Birkas Kohanim they can't go out and lay their hands on everyone's heads, but does this mean that there's no difference if there's actual contact? If by Moshe Rabbeinu Hashem told him that one hand was adequate, and Moshe, out of his own chesed, used two, then did Ephraim and Menashe receive lesser brachos because they each had only one hand? The Yaavetz in the siddur says that he had to do them both at the same time so as not to belittle the second, but the fact remains that each got only one hand. Does it matter? Is the pshat that you have to do the most that is possible, and אונס כמאן דעביד דמי that what you weren't able to do is viewed as if you actually did do it, which would be exactly the diametric opposite of the rule of כל הראוי לבילה אין בילה מעכבת בו וכל שאינו ראוי לבילה בילה מעכבת בו! Is the pshat like Bas Pharaoh, who stretched out her hand even though it was humanly impossible to reach the child, because a person who really cares will do what he can even if it is impossible to accomplish what he wants to accomplish, and what really matters here is the desire to touch the person?
HOWEVER: see below, #7, regarding using the hands in Birkas Kohanim, where most poskim hold that it is essential.
A. Water: Netillas Yadayim Brings Bracha
R’ Shteinman in his Ayeles HaShachar brings the Gemara (Shabbos 62b, and OC 158) that Rav Chisda used to use more than the required measure of water for Netilas Yadayim, and he attributed his receiving bracha to this meritorious behavior. דאמר רב חסדא אנא משאי מלא חפני מיא ויהבו לי מלא חפני טיבותא . But we don't find that it is of any merit to be tovel in a mikva that has more than forty sa'ah of water. What's the difference? Rav Shteinman suggests that the halacha may be based on the specific association of hands with bracha.
This is not sophistry and it is not yeshivisheh obscurantism. It's the best way I can think of saying it. If you can think of a way to make it more clear, please let me know.
Both the Avoda in the Beis Hamikdas and Duchenning requires the hands of Kohanim. But the role of their hands in Duchening is fundamentally different than the role of their hands in Avodas Beis Hamikdash.
6. What Does ושמו את שמי על בני ישראל ואני אברכם Mean?
7. The Machlokes Whether the Kohanim Raising Their Hands is Essential
According to the Mishna Berura in 128:sk50, the majority of Achronim say that if the Kohen does not raise his hands, he does not fulfill the Mitzva of Birkas Kohanim/there is no Bracha. For example, the Pri Megadim (EA121) says that if the Kohen does not raise both hands, it is passul. The Noda BeYehuda (OC 1:5) proves this from the fact that a Kohen with blemished hands, or a Kohen that had killed someone, cannot duchen. If use of the hands was not essential, they could duchen without using their hands. But he brings that the Shevus Yaakov holds that it is kosher outside the Beis Hamikdash. Also, the Radvaz is machshir an amputee.
8. The Kohanim that Cover Their Faces and Hands
The Mor Uktziah in 128 (on the MA SK 54) says that it would be a mitzva to get Kohanim to stop covering their faces and hanging the Tallis over their hands, and also to get the people receiving the Bracha to not cover their faces. He says that a bracha should be given with a direct face-to-face connection. Regarding the hands, he says (starting at the end of the page):
9. I'm Waiting to Hear From You.
I don't have a chiddush to say, or a unifying pshat in all these interesting things and questions. But in my experience, when anomalies occur in groups, there is some concept or rule that joins them, as Reb Chaim says in the Gemara in Chagiga 3b by Shoteh, the rule known to the outside world as Occam's Razor. Or, לכשתמצי לומר, they can be MADE to relate. If you think of something, I would be happy to hear it.