We are aware that they say, "A human is teaching him." The language of the one they refer to is foreign, while this is a clear Arabic language.
Translation endnotes
[16:103] Holy books besides the Quran have been tampered by clergymen. If we compare the Old and New Testaments, the originality of the Quran will become evident. The Quran might report similar historical events, yet it never reports contradictions or silly stories like the ones inserted into the Bible. For instance, compare Quran's 2:93 with the Bible's Exodus 32:20; or compare Quran's 11:40-44 to the Bible's Genesis, Chapters 6-8 and 1Peter 3:18-20; 2Peter 2:5; 2Pe 3:6. Dr. Maurice Bucaille's book, "The Bible, The Quran and Science" contains numerous comparisons between the Quran and the Bible. (See 95:2). We might translate the end of the verse as, "The language of the one they refer to is unintelligible, while this is perfect and clear" See 43:3.