Numbers 23:20

הנה ברך לקחתי BEHOLD, I HAVE RECEIVED COMMANDMENT TO BLESS — You ask me derisively, (v. 17) “What hath the Lord spoken”? I will tell you: I have received an order from Him to bless them. וברך ולא אשיבנה AND HE HAS BLESSED AND I CANNOT REVERSE IT — “He” has blessed them, and “I” cannot reverse this blessing. וברך — This is equivalent to וּבִרֵּךְ. This is the rule of the letter ר, as in (Psalms 74:18): “the enemy blasphemeth”, חֵרֵף like חִרֵּף; and similarly (Psalms 10:3): [ובצע בֵּרֵךְ [נאץ ה׳ (where בֵּרֵךְ is for בִּרֵּךְ), which means, He who praises and blesses the robber (בצע) and says, ‘Do not be afraid, for you will not be punished; peace will be unto you’, he angers (נאץ) God thereby (but see Rashi on this verse where another translation is given). — One cannot say that ברך is a noun, for if it were, it would be voweled in both syllables with Short Patach (our Segol), and its accent would be on the first syllable (בֶּרָךְ) because it is a verb in the Piel conjugation, it is voweled with Short Kametz (our Tzéré) on both syllables, and its accent is on the last syllable.

הִנֵּ֥ה בָרֵ֖ךְ לָקָ֑חְתִּי וּבֵרֵ֖ךְ וְלֹ֥א אֲשִׁיבֶֽנָּה׃

Behold, I am bidden to bless: and he has blessed; and I cannot reverse it.