3 Heb “causeless curse” ( similar) describes an undeserved curse (cf. , ). The Hebrew word translated “causeless” is the adverb from ָחנַן (khanan); it means “without cause; gratuitous.” This proverb is saying that a curse that is uttered will be powerless if that curse is undeserved. It was commonly believed in the ancient world that blessings and curses had power in themselves, that once spoken they were effectual. But scripture makes it clear that the power of a blessing or a curse depends on the power of the one behind it (e.g., Num 22:38; 23:8). A curse would only take effect if the one who declared it had the authority to do so, and he would only do that if the curse was deserved.
4 The has the negative with the verb “to enter; to come” to mean “will not come” (לֹא תָבֹא, lo’ tavo’). This is interpreted to mean “will not come to rest” or “will not come home.” Some commentators have taken the Qere reading of לוֹ (lo) instead, and read it as “will come home to him.” This is also a little difficult; but it gives the idea that an undeserved curse will come [back] to him [who gave it]. Just as a bird will fly around and eventually come home, so will the undeserved curse return on the one who gave it. This is plausible; but there is no referent for the suffix, making it syntactically difficult.