"May Hashem bless you, and guard you: May Hashem shine His face on you, and be gracious to you: May Hashem lift up His countenance upon you, and give you peace." (Bemidbar 6:24 - 26)
If a Cohen does not go to up to bless the congregation when the leader calls out "Cohanim" (before the last Bracha in the Amida) he has missed doing this Mitzva.
Applies to Cohanim, always, everywhere.
Verse: "So shall you bless the children of Israel..." (Bemidbar 6:22)
Source: The Chafetz-Chaim's Sefer haMitzvot haKatzar; Positive Mitzvah 58
Thursday, 19 Tamuz 5770