Bilam's Powerless Blessing
בפסוק ידעתי כו' אשר תברך מבורך ואשר תאור יואר
On the verse, "I have known... that whomever you bless is blessed, and whomever you curse is cursed" (Bamidbar 22:6).
Balak praises Bilam's reputation by quoting that anyone Bilam blesses is blessed and anyone he curses is cursed.
בברכה לא כתיב יבורך
Regarding the blessing, it is not written "he shall be blessed."
The Sfas Emes notes a precise change in the wording: when it comes to blessing, the verse does not use the future-tense form "he shall be blessed" as it does for the curse.
כי באמת אין לרשע זה כח לברך רק לקלל כי טוב עין הוא יבורך ולא רע עין אך מי שאין שולט בו קללותיו ומברכו הוא מבורך באמת והוא סימן שאינו יכול לקללו
For in truth this rasha had no power to bless, only to curse. As the verse says, "One who has a good eye, he shall be blessed" (Mishlei 22:9) -- and not one who has an evil eye. Rather, whoever is not subject to his curses, and he blesses him, that one is truly blessed; and this is a sign that he is unable to curse him.
Bilam, a rasha with an evil eye, truly had no power to bestow blessing at all -- only to curse. So when the verse speaks of one whom Bilam "blesses," it really means a person over whom Bilam's curse has no power; that person is already truly blessed, and Bilam's inability to harm him is itself the proof.
אבל בקללה כתיב יואר כי יכול הוא בכח רע עין שלו לקלל ולא לברך כנ"ל:
But regarding the curse it is written "he shall be cursed," for he does have the power, through his evil eye, to curse and not to bless, as explained above.
By contrast, the curse is stated as an active outcome -- "he shall be cursed" -- because Bilam's evil eye genuinely could bring a curse to bear, whereas blessing was never within his reach.
Summary: The Sfas Emes examines Balak's words to Bilam, "whomever you bless is blessed, and whomever you curse is cursed," and detects a subtle shift in the language: the Torah does not say of the blessing "he shall be blessed" as it does of the curse "he shall be cursed." He explains that a rasha like Bilam, who possesses an evil eye, has no genuine power to bestow blessing -- only one with a good eye can be a source of blessing. Therefore, when the verse speaks of someone whom Bilam "blesses," it really describes a person whom Bilam is simply unable to curse; that very immunity is the sign that the person is already truly blessed. The curse, however, is rendered as an active force -- "he shall be cursed" -- because Bilam's evil eye really could bring a curse to fruition. In short, Bilam's curse carried real force, but blessing lay entirely beyond his power.