|יד לֹא-תְקַלֵּל חֵרֵשׁ--וְלִפְנֵי עִוֵּר, לֹא תִתֵּן מִכְשֹׁל; וְיָרֵאתָ מֵּאֱלֹהֶיךָ, אֲנִי ה.||14 Thou shalt not curse the deaf, nor put a stumbling-block before the blind, but thou shalt fear thy God: I am the LORD.|
You shall not curse a deaf person [From this verse] I know only that [one may not curse] a deaf person. But from where do I know that this [prohibition] includes [cursing] any person [even if he is not deaf]? Therefore, Scripture says, “You shall not curse…among your people.” But if this is so [that this law is not exclusive to deaf people], why does it say here, “a deaf person?” (Exod. 22:27). [The answer is that] just as a deaf person is special insofar as he is alive, likewise, [one is prohibited from cursing] anyone who is alive. This excludes [cursing] a dead person, for he is not alive. — [Torath Kohanim 19:35]Thus, Rashi cites traditional sources, and casts specifically the stumbling block as an idiom. But cursing the deaf he does not cast as an idiom. Rather, it is a prohibition on literally cursing the deaf. There is some back and forth discussion on this matter, and they derive an exclusion to cursing the dead.
You shall not place a stumbling block before a blind person Before a person who is “blind” regarding a matter, you shall not give advice that is improper for him. [For instance,] do not say to someone,“ Sell your field and buy a donkey [with the proceeds], ”while [in truth,] you plan to cheat him since you yourself will take it from him [by lending him money and taking the donkey as collateral. He will not be able to take the field because a previous creditor has a lien on it.] - [Torath Kohanim 19:34]
and you shall fear your God [Why is this mentioned here?] Because this matter [of misadvising someone] is not discernible by people, whether this person had good or evil intentions, and he can avoid [being recriminated by his victim afterwards] by saying, “I meant well!” Therefore, concerning this, it says, “and you shall fear your God,” Who knows your thoughts! Likewise, concerning anything known to the one who does it, but to which no one else is privy, Scripture says, “and you shall fear your God.” - [Torath Kohanim 19:34]
Fine. As a practical matter, I think on the level of peshat I agree a lot with this explanation. That is, I would take both statements idiomatically, perhaps in general or perhaps to something specific in the context of paying a laborer (see the context of the pesukim). But there is validity to both the mashal and the nimshal. From the fact that it brings down the idiom, we can understand that it is a bad thing to curse someone -- anyone. It is just that the deaf person cannot hear and thus know or perhaps defend himself from it. But the fact remains that the underlying assumption is that it is a mean thing to do to anyone. And one can even see how this would not apply to a non-living person, though not through the specific formal mechanism in place (and though this might depend on how one understands cursing). We can even perhaps make some homiletic point here, how the midrash is saying that despite his disability such that he cannot hear, he still is a live human being and is entitled to respect as such.
“You shall not curse…among your people” is actually a partial phrase. It is really venasi beamecha lo saor. Thus, this midrash assumed there was a general principle against cursing everyone, not just a nasi, and then deduces something from the cheresh. On a more peshat-oriented level, we can indeed say that the case of the cheresh informs us about the general case.
לא תקלל חרש וגו ': אזהרה למזיק בסתר ואומר : לא יראני אדם .Here we can say that it fits well with וְיָרֵאתָ מֵּאֱלֹהֶיךָ, אֲנִי ה. Even though man will not see him. Hashem will see and know, even if the blind man and the deaf man don't know that they are being harmed. Shadal appears to take it idiomatically as well -- as about a מזיק בסתר, rather than the specific two cases. And he also relates it to the case of the deaf man, something Rashi does not do. This also is a compelling approach.
Ibn Ezra says וכן לא תקלל חרש בעבור שיש לך כח וכן לפני עור, following a discussion of the sachir. This suggests to me that he does not treat it entirely idiomatically, but perhaps as two more cases along the same lines as the previous. Or maybe it is still entirely an idiom. Regardless, it is a different idiom. Here the theme is powerlessness rather than harming someone in secret.
The Karaite scholar Aharon ben Yosef says as follows: (click on the image to get a larger, readable picture)
He relates it to the context of sachir, which would be somewhat idiomatic. But he leads off with a very literal explanation: The cheresh is mentioned because he does not hear Onaas devarim to be able to take nekama. And the iver does not see it. And Hashem sees, and is able to transform one to the other (make the offender into a blind or deaf person). That is the meaning of וְיָרֵאתָ מֵּאֱלֹהֶיךָ. These are mentioned in the context of the laborer. Why? Perhaps (likely) I am misunderstanding this, or reversing the meaning of שוכר אותו and שכיר, but he says כי אולי יקלל לשוכר אותו ולא פרע שכרו. Interesting how he works in יקלל. Please help me out in the comments in explaining this. It seems he is saying that the laborer will יקלל to the employer and thus the employer will not pay him, as in the previous verse of lo salin peulas sachir. Does יקלל mean hear "treat lightly"? In the context of cheresh, I would guess not. So it is an idiom to teach about the sachir, but within the universe of its own verse it is literal, to the extent the וְיָרֵאתָ מֵּאֱלֹהֶיךָ is a threat to blind or deafen. I'm not sure I buy it.
Now for my own take:
This particular pasuk is a good candidate for discussion. To me, it seems obvious that it is an idiom. And if you would be tempted to take the stumbling block before the blind man literally, the fact that cursing the deaf, another potential idiom, is in close proximity, helps one conclude that the other, too, is an idiom.
Just to think about it. You shall not curse the deaf. Great, but your neighbor you should curse? It is a nice thing to do to stick out your foot to trip up your seeing neighbor?
The idea appears to be that these are even worse, for they have no way of protecting themselves. You put the stumbling block there, and the blind person has no way of knowing about it to take precautionary measures. You curse a deaf person. What does cursing mean? It could that this reflects a view in which there is power to curses. Thus, we see that Bilaam was hired by Balak to curse the Jews, assuming that such a curse will be effective. Or else it means verbally abuse, say hurtful things to. And it probably does fit into the context. But still, the idioms are applicable across the board, e.g. deliberately giving someone bad business advice. And the literal meaning also seems true because the mashal itself has value. That does not necessarily make all of these interpretations Biblical law from a halachic standpoint, but that does not really matter in the present discussion.
Note: Written while severely under the weather. I hope I don't ramble to much, and that I make some sense.