This important blessing, so well known and used with gratitude by Judeo-Christian traditions, is ubiquitous in many services. But it’s curious. God is usually responsible for blessing. Yet here it is Aaron and his sons, the priests, who are asked to do the blessing.

In many traditional synagogues, Cohanim duchen and offer this blessing. So powerful a childhood memory was this for Leonard Nimoy, the actor who played Spock in Star Trek ,that he took the image of the Cohen with separated fingers as his standard and, what became iconic, greeting.

It’s powerful stuff. But controversial, too. Unusually, these blessings are introduced through a command to the priests, “Thus you shall bless them”. This has dismayed classical commentators. Were the priests invoking divine blessing as a parent might or were they themselves engaged in blessing Israel?

The majority understanding is that the priests invoked the divine blessing, a supplication to God. Rabbi Samson Raphael Hirsch insists the Torah did not suggest a priestly caste with free power to bless. Rather, the priest had clear and distinct instructions to invoke this specific blessing.

Although priesthood is no longer, its legacy survives in many parts of the Jewish world and Cohen and Levite still have roles in liturgical life.

Progressive synagogues have chosen a democratic attitude to the community, where all are Israel and all those who act as shaliach tzibbur have the right and responsibility to invoke this blessing (just as Aaron and his sons). Rabbi John Rayner called this blessing, when used liturgically, “the threefold benediction of the Torah” as an alternative to its priestly title, drawing out the threefold blessing of protection, graciousness and peace. And it’s that which is invoked by mother, father, rabbi or those leading prayers, just as the Torah may have intended.