B"H
In the curses Hashem tells the snake it says "because you have done this, you are cursed from all beasts of the field..", without specifying exactly what that means.
If you would say that it refers to the snake's legs being cut off, then why does it mention specifically later "on your stomach, you shall walk" (as if to imply a separate idea)?
One might say that it means that it's power of speech would be taken, but why doesn't it say that explicitly, like it says by the other curses?
And if it doesn't mean that, then where does it say that the power of speech was taken from him?
Obviously snakes {which are all descended from the first snake, who originally did talk} don't talk now, so at some point in time snakes must have lost their power of speech, and seemingly it would make sense that it happened to the very first snake itself, but I haven't found any verses or explanations of Rashi which specifically say that it's speech was removed as part of the curses.
And even if it would be obviously implied that it's speech was removed as a part of all of the other curses (because, when and why else?) but the question (at least) remains:
Why didn't Hashem tell the snake that it's power of speech would be removed, just like the other curses were explicitly told to it?
This question and answer https://judaism.stackexchange.com/a/40980/31763 touches on the idea, but doesn't explain why the statement of "you're cursed from all etc.." wasn't specifically said to include the loss of the snake's voice (it only explains how it was, not why).
