Priestly Blessing - in Hebrew Law and Custom

In Hebrew Law and Custom

• Only Kohanim (i.e., adult - age 13 or older - males in direct patrilineal descent from Aaron) can perform the Priestly Benediction. And the blessing should be performed only in the presence of a minyan (quorum of ten adult males) - even if the Kohanim themselves must be included for a total of ten.
• Tradition prohibits a Kohen from reciting the blessing while under the influence of alcohol, or in the period immediately following the death of a close relative.
• All Kohanim present are obligated to participate, unless disqualified in some way. If a Kohen does not wish to participate, he must leave the sanctuary for the duration of the blessing. A Kohen may be disqualified by, e.g., having imbibed too much alcohol, having a severe speech impediment, blindness, having taken a human life, having married a disqualifying wife (such as a divorcee), the recent death of a close relation.
• A Kohen who is on bad terms with the congregation or who is unwilling to perform the ritual should not perform it.
• It is customary that, once the Kohanim are assembled on the platform, the canter or prayer leader will prompt them by reciting each word of the blessing and the Kohanim will then repeat that word. This custom is especially followed if only one kohen is available to give the blessing. Apparently this prompting is done to avoid errors or embarrassment if any of the kohanim should be ignorant of the words of the recitation. However, if there are a number of kohanim, they may say the first word of the blessing ("Yevorekhekhaw") without the prompting, presumably to demonstrate their familiarity with the ritual.
• If the prayer leader is a Kohen himself, he does not prompt the other Kohanim in the blessing. Instead, a non-Kohen is designated with that task, and the leader remains silent.
• The Mishnah records advice that a person who is troubled by a dream should reflect on it when the Kohanim recite their blessing. This practice is still done in many Orthodox communities. It is also recited at bedtime. Both uses derive from the Song of Songs 3:7-8, telling of 60 armed guards surrounding Solomon's bedchamber to protect him from "night terrors"; the 60 letters in the text of the blessing similarly defend against night terrors.
• In many traditional Jewish communities it is the custom for congregants to spread their tallitot over their own heads during the blessing and not look at the Kohanim. If a man has children, they will come under his tallit to be blessed, even if they are quite old.
• This blessing is also used by some parents to bless their children on Friday night before the beginning of the Shabbat meal. Some rabbis will say the blessing to a boy at his bar mitzvah or to a girl at her bat mitzvah. It is usually prefaced, for boys with a request for God to make the child like Ephraim and Manasseh These were the two sons of Joseph) who are remembered because according to tradition, they never fought with one another. For girls the traditional request is God to make them like Sarah, Rebecca, Rachel and Leah, the Matriarchs of the Jewish people.
• It also may be said before a long journey, and some people will write it out and wear/keep it as an amulet. It is often used in the liturgy as the first section of Torah to be read in the morning after reciting the blessing before studying Torah.
• In the case where no Kohanim are present in the synagogue (but there still is a minyan) the hazzan will read the prayer verse by verse, and the congregation will respond after each verse with "ken yehi ratzon" (May it be God's Will). This response is used instead of "Amen", because the hazzan is merely "mentioning" the blessing, essentially quoting it rather than actually performing the ritual. However, some congregations (including Chabad) do indeed respond "Amen". This response is also employed on days and times when the Amidah is repeated but the Kohanim do not recite the priestly blessing. However, according to Abudirham, since the Priestly Blessing is not a conventional benediction (that would begin with "Blessed are Thou ..."), but rather a prayer for peace, ken yehi ratzon is the more appropriate response at all times.