יי spoke to Moses: Speak to Aaron and his sons: Thus shall you bless the people of Israel. Say to them:
יי bless you and protect you!
יי deal kindly and graciously with you!
יי bestow [divine] favor upon you and grant you peace! Thus they shall link My name with the people of Israel, and I will bless them.

In the morning, Musaf, and Ne'ilah services, the priests recite the priestly blessing. They do not recite the priestly blessing in the Minchah service, because, by the time of the Minchah service, all the people have eaten. The possibility exists that the priests would have drunken wine, and it is forbidden to recite the priestly blessing while intoxicated.
Even on a fast day, the priestly blessings are not recited during the Minchah service. This decree [was instituted,] lest [people fail to differentiate between] the Minchah service of a fast day and the Minchah service of an ordinary day.

When does the above apply? On fast days when both Minchah and Ne'ilah are recited - i.e., Yom Kippur and communal fasts [declared because of distress]. However, on a fast day on which Ne'ilah is not recited - e.g., Tish'ah B'Av or the seventeenth of Tammuz - since the Minchah service is recited close to sunset, it resembles Ne'ilah and will not be confused with an ordinary Minchah service. Therefore, the priestly blessing is recited during it.
If a priest transgressed and ascended to the platform during the Minchah service of Yom Kippur, since it is known that there is no possibility of drunkenness on that day, he may recite the priestly blessing, and he is not required to descend because of the suspicion [that might be aroused], so that people do not say, "He is of blemished lineage. Therefore, they forced him to descend."

How is the priestly blessing recited outside the Temple? When the leader of the congregation reaches the blessing R'tzey, when he recites the word R'tzey all the priests in the synagogue leave their places, proceed forward, and ascend the duchan.
They stand there, facing the heichal, with their backs to the congregation. They hold their fingers closed, against their palms, until the leader of the congregation completes the blessing Modim. [Then,] they turn their faces to the people, spread out their fingers, lift up their hands shoulder high, and begin reciting, Y'varechecha....
The leader of the congregation reads [the blessing] to them, word for word, and they respond after him [as can be inferred from Numbers 6:23: "This is how you should bless the children of Israel:] 'Say to them...;’” [i.e., the priests do not bless until one] "says to them."
When [the priests] conclude the first verse, all the people answer "Amen." The leader of the congregation reads [the priests] the second verse, word for word, and they respond after him until they complete the second verse. The people respond "Amen." The same applies regarding the third verse.

When the priests conclude the recitation of [these] three verses, the leader of the congregation begins the final blessing of the Shemoneh Esreh, Sim shalom. The priests turn their faces to the ark and close their fingers. They remain standing on the duchan until the leader of the congregation concludes the blessing, [and then] return to their places.

When the priests bless the people, they should not look at them or divert their attention. Rather, their eyes should be directed towards the earth like one standing in prayer.
A person should not look at the priests' faces while they are blessing the people, lest they divert their attention. Rather, all the people should listen attentively to the blessing; they should [stand] face to face with the priests, without looking at their faces.

If only one priest is blessing the people, he should begin reciting the blessing alone. [Afterwards,] the leader of the congregation reads [the blessings] to him, word for word, as mentioned.
If there are two or more [priests blessing the people], they do not begin reciting the blessing until the leader of the congregation calls them, saying "Kohanim." They answer and respond Y'varechecha, and then he reads [the blessings] to them, word for word, in the manner described above.

Wherever the priestly blessing is recited, it is recited only in the holy tongue, as [implied by Numbers 6:23]: "This is how you should bless the children of Israel."
We have learned the following [instructions] from the tradition [passed on] from Moses, our teacher, may he rest in peace:
"This is how you should bless" - while standing.
"This is how you should bless" - raising your hands.
"This is how you should bless" - in the holy tongue.
"This is how you should bless" - face to face.
"This is how you should bless" - in a loud voice.
"This is how you should bless" - mentioning [God's] explicit name; the latter [applying only] when one is in the Temple, as explained.

When the priests turn their faces to the community to bless them, and when they turn their faces from the community after blessing [them], they should turn only to the right. Similarly, any turns which a person makes should always be to the right.

There are six factors that prevent [a priest] from reciting the priestly blessings: [an inability] to pronounce [the blessings properly], physical deformities, transgressions, [lack of] maturity, intoxication, and the ritual impurity of [the priest's] hands.
[An inability] to pronounce [the blessings properly]: What is implied? Those who cannot articulate the letters properly - e.g., those who read an aleph as an ayin and an ayin as an aleph, or who pronounce shibbolet as sibbolet and the like - should not recite the priestly blessings.
Similarly, a stutterer or one who speaks unclearly, whose words cannot be understood by everyone, should not recite the priestly blessing.

Transgressions: What is implied? A priest who killed someone should never recite the priestly blessings, even if he repents, as [implied by Isaiah 1:15 which] states: "Your hands are full of blood," and states: "When you spread out your hands, I will hide My eyes from you."
A priest who served false gods, even if he was compelled to do so or did so inadvertently - though he has repented - may never recite the priestly blessing, as [can be inferred from II Kings 23:9, which] states: "However, the priests of the high places shall not ascend [to God's altar in Jerusalem]." [The recitation of the priestly] blessings is equated to service [in the Temple], as [Deuteronomy 10:8] states: "to serve Him and to bless in His name."
Similarly, a priest who converted to the worship of false gods - even though he repents - may never recite the priestly blessing. Other transgressions do not prevent [a priest from blessing the people].

The ritual impurity of [the priest's] hands: What is implied? A priest who did not wash his hands should not recite the priestly blessing. Rather, he should wash his hands to the wrist, as is done when sanctifying the hands for the service in the Temple, as [Psalms 134:2] states: "Raise up your hands [in] holiness and bless God."
A challal does not recite the priestly blessing, for he is not a priest.

A priest who does not have any of the factors which hinder the recitation of the priestly blessings mentioned above should recite the priestly blessing, even though he is not a wise man or careful in his observance of the mitzvot. [This applies] even though the people spread unwholesome gossip about him, or his business dealings are not ethical.
He should not be prevented from [reciting the priestly blessings] because [reciting these blessings] is a positive mitzvah incumbent on each priest who is fit to recite them. We do not tell a wicked person: Increase your wickedness [by] failing to perform mitzvot.

Do not wonder: "What good will come from the blessing of this simple person?" for the reception of the blessings is not dependent on the priests, but on the Holy One, blessed be He, as [Numbers 6:27] states: "And they shall set My name upon the children of Israel, and I shall bless them." The priests perform the mitzvah with which they were commanded, and God, in His mercies, will bless Israel as He desires.

The people standing behind the priests are not included in the blessing. Those standing at their sides are included in the blessing. [Even] if there is a partition - even an iron wall - between the priests and the people who are being blessed, since they are facing the priests, they are included in the blessing.

Any priest who does not ascend to the duchan - even though he neglects [the performance] of [only] one commandment - is considered as if he violated three positive commandments, as [Numbers 6:23-27] states: "This is how you shall bless the children of Israel," "Say to them," "And you shall set My name..."
Any priest who does not recite the priestly blessing will not be blessed, and any priest who blesses [the people] will be blessed, as [Genesis 12:3] states: "And I will bless those who bless you."

When the Kohanim do not want to ascend to the platform, they are not required to stay outside the synagogue except during the time when the chazzan calls "Kohanim." Nevertheless, so that people shouldn't say that they are disqualified, it is customary that they do not enter the synagogue until Birkat Kohanim is completed.

Kohanim may not ascend to the platform in shoes, but in socks it is permitted. (Some are stringent if they [the socks] are made of leather) (Aguda, Chapter "HaKoreh et HaMegilla" [Megillah Chapter 2]) (and they practice leniently in a few places).)

When the prayer leader starts [the blessing] "R'tzei", every Kohen that is in the synagogue must uproot from [that Kohen's] place to go up to the platform, and even if [the Kohen] doesn't arrive there until the prayer leader concludes R'tzei, that's fine. But if [the Kohen] did not uproot [the Kohen's] feet at R'tzei, [that Kohen] may no longer go up.