Nedarim 5 - 11
Who Comes First?
If one says to his friend, "let us get up early and study this subject together," it is incumbent on him to be there first. Rabbi Gidal cited this halacha in the name of the Sage Rav whose source was the account of an encounter between Hashem and the Prophet Yechezkel (3:22-23): "He said to me, 'Go out to the valley where I shall speak to you.' I arose and went out to the valley and, behold, the Glory of Hashem stood there."
Two important lessons are communicated in this statement of Rav. If one makes a verbal commitment to study Torah or to do any other mitzvah, even though he did not make a formal vow, he is obligated to fulfill that commitment just as one who makes a verbal commitment to give a sum to charity is obligated to do so (Rosh Hashana 6a). Secondly, if he undertook to do that studying with a partner he must be the first to appear at their designated rendezvous, because it was he who took the initiative in suggesting that project. This we learn from the fact that Hashem, having initiated the encounter with the prophet, appeared at the designated meeting before the prophet.
In his footnotes on the Talmud, Rabbi Akiva Eiger calls our attention to a passage in Chumash and Rashi's commentary on it. The Torah tells us (Shemot 19:16) that on the morning designated for the Jews to receive the Torah at Sinai, the Presence of Hashem preceded the people to this historic rendezvous. Although in human relations it is customary for the disciple to wait for the master, Rashi comments, here Hashem waited for the people. He then parallels this to the aforementioned encounter with Yechezkel where once again Hashem waited for His disciple.
The perspective of Hashem's coming first, based on the Midrash quoted by the Iyun Yaakov, that it was intended as an expression of the humbleness with which Hashem conducts Himself in relation to His creation, seems to run counter to the approach of Rav which draws from the incident in Yechezkel a halachic norm.
We may suggest that the two approaches are complementary rather than contradictory. As Iyun Yaakov points out, Rav's rule applies only to two friends of equal status. Only then must the initiator appear first. Should the master initiate such a meeting with the disciples, however, it is still the disciple who must wait for the master out of deference to his honor. Hashem, in His extraordinary humbleness, waived the honor due Him and related to Yechezkel as one would with a colleague. But why did Hashem insist on appearing first? This obviously came to teach us that the colleague who is the initiator of the project must be there first.
But why did Rav have to draw upon the Yechezkel incident if the same lesson could have been derived from Hashem waiting for His people at Sinai? Perhaps out of consideration for an entire nation Hashem, in His humbleness, assumed the status of disciple rather than master or even colleague. This would therefore prove only that a disciple must wait for his master and not that an initiating colleague must wait for his partner, something we are able to learn from the rendezvous with Yechezkel.
Shalom Aleichem -- Aleichem Shalom
When one Jew meets another he traditionally greets him with "Shalom Aleichem," and the other returns the greeting with "Aleichem Shalom."
A possible source for this style of exchanging greetings is our gemara. When one wishes to dedicate something as a sacrifice to be offered to Heaven he should not say "This shall be to Hashem an olah, to Hashem a mincha, to Hashem a todah, to Hashem a shelamim." He should rather first state the nature of the sacrifice and then mention the Name of Hashem. Rabbi Shimon derives this from the term used by the Torah at the very beginning of the laws of offerings (Vayikra 1:2) "an offering to Hashem." The reason for this caution is that if one begins his declaration with the sacred Name of Hashem, there is a danger that he may not complete his statement and thus be guilty of the serious sin of involuntarily taking Hashem's Name in vain.
The gemara does not mention what danger is involved. The general assumption is that there is a danger that one who first says Hashem's Name may die suddenly and be unable to complete the statement he intended to make.
Shalom is also considered one of Hashem's Names (Mesechta Shabbat 10b) and caution must be exercised in using it. The one who initiates the greeting need not fear that he will die before completing it and thus be guilty of using that Name in vain, because the merit of initiating a greeting to a fellow Jew will protect him from sudden death in mid-greeting. The one responding, however, is involved only in a courtesy and must therefore take the precaution of saying the "Aleichem" before the "Shalom," lest his use of Hashem's Name be aborted and rendered as improper usage.
The "shalom" used in modern Israeli society does not seem to have any relationship with this concept of greeting someone with the Name of Hashem, and it is nothing more than the "peace" greeting used in other societies.