16:103 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.*
Edip-Layth (Quran: A Reformist Translation)
Dictionaries
Ejtaal Arabic Almanac: Lane's Lexicon, Hans Wehr, Lisan al-Arab and others
for, [O Muhammad,] thou hast never been able to recite any divine writ ere this one [was revealed], nor didst thou ever transcribe one with your own hand* or else, they who try to disprove the truth [of thy revelation] might indeed have had cause to doubt [it].*