In this Parsha, the Torah records the text of the Birchas Kohanim (במדבר ו':כ"ד-כ"ו). It is somewhat unusual that the commandment to bless the Jewish nation and the precise formulation of the text used for that blessing would first be recorded in this Parsha. Earlier in the Torah, when describing the completion of the dedication of the Mishkan in Parshas Shemini, the Torah states "וישא אהרן את ידו אל העם ויברכם," "Aharon raised his hands towards the people and blessed them" (ויקרא ט':כ"ב). Rashi (שם בד"ה ויברכם) states that Birchas Kohanim was the text used in this blessing. Although the narrative in our Parsha happens to be describing the precise day which is discussed there in Parshas Shemini, namely, the day of the dedication of the Mizbeiach, perhaps one might nevertheless have expected the text of the blessing recited there by Aharon to be formulated prior to its first official use, meaning in, or prior to, Parshas Shemini. Apparently, the Torah wished to present the full text here in our Parsha where other events relating to that special day of dedication are presented in fuller detail.
It is interesting to note that the Torah introduces the commandment to bless Bnai Yisrael by using the word "כה," as the Posuk states "כה תברכו את בני ישראל אמור להם," "so shall you bless Bnai Yisrael, say to them" (במדבר שם פסוק כ"ג). The Midrash states that in the merit of three other episodes where the word "כה" is used in the Torah, Bnai Yisrael merited Birchas Kohanim which is introduced with the word "כה." The Pesukim which use the word "כה," as referred to by the Midrash, are as follows: "כה יהיה זרעך," "so shall be your children" (בראשית ט"ו:ה'), "ואני והנער נלכה עד כה...," "and the young man and I will go to a certain place" (שם כ"ב:ה'), and "כה תאמר לבית יעקב ותגיד לבני ישראל," "so shall you say to the house of Yaakov and tell to Bnai Yisrael" (שמות י"ט:ג'). These three Pesukim concern, respectively, the promise made to Avraham Avinu at the Bris Bein HaBesarim, Akeidas Yitzchak, and the introduction to Mattan Torah. What exactly does the Midrash wish to communicate by highlighting the use of the word "כה" in these specific places?
One may suggest that perhaps Chazal wished to outline the prerequisites for experiencing a true Beracha. The notion of Beracha is very often used in the context of fertility and procreation. For example, we find the very first Beracha back in Parshas Bereishis, where the Torah states that Hashem blessed Adam and Chavah and told them to be fruitful and multiply (בראשית א':כ"ב). In Parshas Noach as well, the Torah records that a similar Beracha was given to mankind, as Noach and his family were told that they should be fruitful and multiply (שם ט':א'). This would seem to indicate that the greatest Beracha that man can experience is producing children who will perpetuate one's own beliefs, values, and commitment.
This charge is the essence of the message represented by the first "כה" used in connection with Avraham. When he was told "כה יהיה זרעך," "so shall be your children," the Beracha was that his children would reflect the tenets set by the Bris Bein HaBesarim, namely, that Hashem will be their G-d, and they will be His children. The next two times the word כה"" is used, it is used to present the ingredients necessary to assure the success of this relationship. The fulfillment of the commitment made at the Bris Bein HaBesarim obviously requires enormous sacrifice. The paradigm of self-sacrifice is the commitment expressed by Avraham and Yitzchak as they approached Har HaMoriah to perform the Akeidah, hence the use of the word "כה" in that context. The other key to fulfillment of the commitment made at the Bris Bein HaBesarim is the endearment of each Jew to each and every principle of the Torah. The word "כה" is thus used in connection with Mattan Torah as well.
If one recognizes that the successful transmission of the Mesorah, hinted at by the Bris Bein HaBesarim, is our greatest challenge and yet our greatest source of blessing, then we must all be prepared to make the type of sacrifice that may be entailed, both in terms of self-sacrifice and in terms of commitment to the Torah. Only then will we be able to become truly blessed and merit the fulfillment of the words of Birchas Kohanim, introduced by the words "כה תברכו את בני ישראל," "so shall you bless Bnai Yisrael."