“And if We had sent it down to some of the non-Arabs” (Al-Shu‘ara: 198). He says: If We had sent it down in a non-Arabic language, they would not have understood it.
Muhammad says: "Al-A‘jamin" (non-Arabs) is the plural of "A‘jam," and the feminine is "‘Ajma’." It is said: a man is "A‘jam" if there is a deficiency (or foreignness) in his speech, even if he is of Arab lineage. And a man is "‘Ajami" if he is from the non-Arabs, even if he is eloquent in speech.
﴿وَلَوْ نَزَّلْنَاهُ عَلَى بَعْضِ الأَعْجَمِينَ﴾ يَقُولُ: لَوْ أَنْزَلْنَاهُ بِلِسَانٍ أَعْجَمِيٍّ إِذًا لَمْ يَفْقَهُوهُ.
قَالَ مُحَمَّدٌ: الأعجمين جَمْعُ أَعْجَمَ، وَالْأُنْثَى عَجْمَاءُ؛ يُقَالُ: رَجُلٌ أَعْجَمُ؛ إِذَا كَانَتْ فِي لِسَانِهِ عُجْمَةٌ، وَإِنْ كَانَ عَرَبِيَّ اللِّسَانِ، وَرَجُلٌ أَعْجَمِيٌّ إِذَا كَانَ مِنَ الْعَجَمِ وَإِنْ كَانَ فَصِيحُ اللِّسَان.