Quran english an nahl 103

ولقد نعلم أنهم يقولون إنما يعلمه بشر لسان الذي يلحدون إليه أعجمي وهذا لسان عربي مبين

Walaqad naAAlamu annahum yaqooloona innamayuAAallimuhu basharun lisanu allathee yulhidoonailayhi aAAjamiyyun wahatha lisanun AAarabiyyunmubeen

 
Sahih International
And We certainly know that they say, “It is only a human being who teaches the Prophet.” The tongue of the one they refer to is foreign, and this Qur’an is [in] a clear Arabic language.
Muhsin Khan
And indeed We know that they (polytheists and pagans) say: “It is only a human being who teaches him (Muhammad SAW).” The tongue of the man they refer to is foreign, while this (the Quran) is a clear Arabic tongue.
Pickthall
And We know well that they say: Only a man teacheth him. The speech of him at whom they falsely hint is outlandish, and this is clear Arabic speech.
Yusuf Ali
We know indeed that they say, “It is a man that teaches him.” The tongue of him they wickedly point to is notably foreign, while this is Arabic, pure and clear.
Shakir
And certainly We know that they say: Only a mortal teaches him. The tongue of him whom they reproach is barbarous, and this is clear Arabic tongue.
Dr. Ghali
And indeed We already know that they say, “Surely only a mortal is teaching him.” The tongue (i.e., the language) of him about whom they blaspheme is foreign, and this is an evident Arabic tongue.