Ash-Shu'araa • EN-TAFSIR-IBN-ABBAS
﴿ بِلِسَانٍ عَرَبِىٍّۢ مُّبِينٍۢ ﴾
“in the clear Arabic tongue.”
(In plain Arabic speech) He says: the Qur'an is in the Arabic usage; it is also said that this means: inform them, O Muhammad, using their own language.