Kedoshim

You shall not insult the deaf, or place a stumbling block before the blind. You shall fear your God: I am the Lord.

19:14

At this point the Torah warns that one must not cause distress to one’s fellow by undermining his dignity, his self image and the image he enjoys among his peers…even a damage that the deaf person does not become aware of…even indirect damage. Who knows if the blind will trip over the obstacle?

Sforno (16^th Century)

Sometimes…the desire for vengeance will not be strong, so that he will find relief in uttering angry imprecations and curses, even though the other would not listen to them if he were present. It is well known that hot-tempered…persons find relief in this way from the annoyance caused by trivial offenses, though the offender is not aware of their wrath and does not hear their fulminations. Now we might suppose that the Torah, in forbidding us to curse an Israelite, was moved by the shame and the pain that the curse would cause him when he heard it, but that there is no sin in cursing the deaf, who cannot hear and therefore cannot feel hurt…

Maimonides (12^th Century)

Although we fail to comprehend how a curse affects the victim, the power of words in this context, the fear of curses is common both among Jews and Gentiles…we venture to suggest that since man’s articulate soul belongs to Heaven…it has the power to affect things beyond its confines. Hence…the pronouncements of the devout materialize in accordance with the substance of the human soul and its communion with the spirit of the righteous and pious in the upper spheres. This is common knowledge among the learned…In Maimonides view, it seems, no harm can come to a person from a curse…Indeed, we accept all our masters’ teachings, though our exposition appeals to us more.

Sefer Hachinuch (15^th Century)

The Samaritans read it literally, i.e. that it is forbidden to trip up the blind. This is correct, hence the prohibition to uncover or dig a hole in a public thoroughfare…thus the prohibition, “nor put a stumbling block…” stands as it is…but it also covers the misleading of the mentally, emotionally, or willfully “blind.”

Meshekh Hochmah (19^th Century)

Rav Natan said: Whence that a man should not serve wine to a Nazirite or flesh from a living animal to a gentile? From the text, “You shall not put a stumbling block before the blind…” Rav Yehudah said in the name of Rav: Whoever has money and lends it without witnesses violates the prohibition of “You shall not put a stumbling block before the blind…”

Pesachim 22b (6^th Century)

Do not offer wrong counsel to one blind to the consequences…do not advise him to sell his field and buy a donkey, and then by subterfuge take hold of it. Since it is not given to humans but only to God to know whether the advice was given in good or bad faith, the Torah warns us to fear God. Whenever this phrase appears, it refers to something entrusted to the conscience of the individual and unknown to anyone else.

Rashi (11^th Century)