Menachot 90 - 96
A Two-Handed Complement
When an individual offered a sacrifice in the Beit Hamikdash in most cases he was required to complement the sacrificial service with semicha by placing his two hands on the head of the animal to be sacrificed. The challenge in finding a source for this requirement of using two hands arises from the fact that in regard to all the sacrifices where the Torah mentions semicha, the singular form is used for "hand," which would indicate that only one hand is needed for this ritual.
The Sage Reish Lakish solved this mystery by pointing to the passage in the Torah chapter dealing with the service performed by the Kohen Gadol on Yom Kippur in the Beit Hamikdash. "Aharon shall place his two yado" (Vayikra 16:21) is how it is written in the Torah. The word yado, however, means his one hand, which is a contradiction to the word "two" preceding it. Our tradition is to indeed pronounce the word as yadav, which is the plural form of hand, and makes it consistent with the word two preceding it. But if the Torah made a point of having the word written in the singular it taught us that just as here the singular form really meant both hands, so too wherever we find the singular form of hand it really means two.
Rabbi Elazar heard this brilliant solution from Reish Lakish and repeated it in the Beit Medrish study hall without quoting it in his name. This upset Reish Lakish and he decided to challenge Rabbi Elazars understanding of the point he had made. If even the singular form for hand always means two, he asked him, why did the Torah write it in plural form in 24 different places? It was only after he felt that he had put Rabbi Elazar in his place did Reish Lakish provide the answer to this question. The rule that he had established regarding the singular form of hand meaning two was limited to where the Torah spoke of placing a hand on an animal. Everywhere else this would not apply, so that where the Torah wished to speak of two hands it had to use the plural form.
A dialogue between King David and the Kohen Gadol Achimelech is the subject of much discussion in our gemara because of its possible ramifications for the laws concerning the preparations of the showbreads on the table of the Sanctuary.
The background of this dialogue was the flight of David from King Saul, who viewed him as a threat to his throne and sought to slay him. In a desperate state of hunger he arrived at the city of Nov where the Mishkan sanctuary stood and asked Achimelech for five loaves of bread or whatever else he had on hand. Achimelech informed him that he had only sacred bread "and the kohen gave him sacred bread for there was no bread there but showbread that had been removed from before G-d." (Shmuel I 21:7)
Nov was populated only by kohanim, whose food consisted of terumah, which is forbidden to a non-kohen. There was therefore no permissible food available to alleviate the life-threatening hunger that had seized David. In such circumstances one may eat forbidden food to save his life but must try to survive on the variety with the least degree of sin. Eating terumah as a non-kohen is punishable by premature death, while eating the showbreads is punishable only by lashes. David therefore asked Achimelech for the five showbread loaves which are his portion as Kohen Gadol. He was pleased to hear from Achimelech that the loaves he offered him had already been removed from the table and were available for consumption by the kohanim, for this meant that the additional ban of meilah stealing something belonging to the Sanctuary no longer applied. But David did point out to Achimelech that even if he had been compelled to take the showbreads off the table and be guilty of meilah as well, he would have been justified in doing so in order to save his life.