"A believer is not harmed by the same stone twice."
Leaving aside the issue with the definite article, this is not the same hadith. The Arabic has: "The Believer is not stung from the same hole twice."
A similar idea maybe, but an entirely different hadith. My point in detailing this mix-up is A.) one always has to be wary of translations even if it is an official translation and B.) these mix-ups are not always so insignificant.
Now, my Arabic is far from perfect - my speaking resembles an illiterate Bedouin (mostly because these are the people I first learned to speak with), my transliteration needs loads of work as does my work on vowelling and editing texts - and it is something that I will be studying for the rest of my life.
One never really stops being an Arabic student. But I take comfort in a quote a good friend, who has the type of linguistic skills that inspire dark and jealous thoughts among fellow academics, often recited at qat chews: "The first ten years of Arabic are the hardest." His source, of course, was none other than A.J. Arberry.