(I bear witness that there is no god but Allah); is the letter (an) with a shaddah or with a sukun?

Q: A. S. A. from Kuwait says in his question: I hear some people saying in the tashahhud: "I bear witness that there is no god but Allah" — with a shaddah on the an — and some say: "I bear witness that there is no god but Allah" — with a sukun on the an. Which is correct? Please inform us, may Allah reward you, O Shaykh.
A: The correct form is the sukun, and the meaning is: "I bear witness that there is no god but Allah." However, the language of the Arabs in such cases is to place a sukun on the nun and assimilate it into the lam because the meaning is clear. If one places a shaddah on the nun and includes the hah, there is no blame in that, by saying: "I bear witness that there is no god but Allah." But using the wording reported in the hadiths from the Prophet (peace and blessings be upon him), which is to lighten the nun and assimilate it into the lam, is more preferable and better. And success is from Allah.