Yahwism knows traditional blessings, pronounced by priests during worship at the Tabernacle or in the Temple, in which the name of God was always heard. At some point...
Yahwism knows traditional blessings, pronounced by priests during worship at the Tabernacle or in the Temple, in which the name of God was always heard. At some point they came to be treated as traditional ritual formulas, but originally all these blessings had their own meaning and purpose.
Such are the blessings we see in the Book of Numbers. In antiquity, the sacred name was generally treated in a special way: it was thought that the name by which God reveals Himself to a person, if pronounced, unites the person with God. Pagans looked at the matter in the same way, and sacred names in the pagan world were often even credited with magical properties.
Yahwism, however, did not involve any magic: the point was the intention that a person directs toward God when calling Him by name. To use sacred names casually, in passing, for rhetorical effect or out of habit, is a violation of the third commandment of the Decalogue, and in ancient Israel this was well understood.
What, then, is a blessing? In its original sense, the corresponding Hebrew word means the transmission by the one blessing of his own (usually supernatural) power to the one being blessed. When God blesses a person, He gives that person His power, and when the priests bless the people, they wish for the people that God, before whom they have just stood, would give them His power.
This power can preserve and protect, especially if God shows a person His face. To meet God face to face meant to experience personal communion with God; such an experience has been known in every age. But this meeting could bring a person not only joy: after all, a sinful person appeared before God as he was, and the outcome of the meeting could be highly unexpected for him.
That is why the traditional ritual formulas include words about peace and mercy: both were absolutely necessary for a sinful person so that a face-to-face meeting with God would not turn into a curse for him instead of a blessing.
Of course, God never curses a person for his sins; otherwise no one would have any chance of salvation. But a meeting with God is always a trial for a person as well, not only joy, and the traditional blessings spoken by the priests also included a request that the meeting with God would become for those being blessed not destruction, but spiritual renewal.