Commentary for Numbers 6:23

אמור is infinitive. Similar forms are זכור (Exodus 20:8), שמור (Deuteronomy 5:12); in O. F. disant, (English = saying).

SPEAK UNTO AARON AND UNTO HIS SONS, SAYING: THUS YE SHALL BLESS. I have already mentioned in Seder Vayehi Bayom Ha’shemini¹¹¹Leviticus 9:1. The verse referred to is ibid., 22. that He commanded Aaron to lift up his hands towards the people and bless them on that day [i.e., the eighth day of the initiation of the priests, which was the day of the final erection of the Tabernacle], and here He commanded Aaron and his sons to do so throughout the generations, and He explained what the blessing was with which they are to bless them. He mentioned this blessing in connection with the setting up of the Tabernacle [discussed in the next chapter], for there the Eternal commanded the blessing, even life forever,¹¹²Psalms 133:3. just as our Rabbis have said:¹¹³Sotah 38 a-b. “In the Sanctuary [the priests pronounced the blessing] using the Divine Name [i.e., the Tetragrammaton],¹¹⁴See in Vol. II, p. 18, Note 84. but in the provinces by a substitute Name. In the Sanctuary they pronounced it as a single blessing, but in the provinces [it was pronounced] as three blessings” [the people responding “Amen” to each of the three verses which comprise the priestly blessing], for the blessing in the Sanctuary was singled out by being pronounced with the Proper Name of G-d [i.e., the Tetragrammaton].

דבר אל אהרון ואל בניו, "speak to Aaron and his sons, etc." Why did the Torah repeat the word לאמור in this verse? Perhaps the Torah was afraid that the blessing described here was something that the priests could pronounce but were not obligated to pronounce. The Torah wanted to make sure that although the word כה at the beginning might be construed as something to be performed voluntarily, i.e. "if you bless you shall keep to this formula," the priests should know it is a positive commandment to bless the Israelites. The repeated use of the word לאמור may also mean that the commandment did not only apply to Aaron and his sons but to the priests in all subsequent generations. There is also an implied compliment to the priests here, i.e. the priests are privileged by G'd to transmit His blessing to the people by pronouncing G'd's wording.