Yehudah ibn Quraysh was a rabbi of the late ninth/early tenth century from Tahert (modern Tiaret, in Algeria.) Shocked to hear that the Jews of Fez in Morocco were neglecting the study of the Targum (an Aramaic translation of the Bible), he wrote a letter to them intended to establish that they could not and should not get by on the Hebrew alone – because other languages, especially Aramaic and Arabic, are essential in elucidating the Hebrew. In the process, he casually noted most of the correct sound correspondences between Hebrew and Arabic, and ended up writing what amounts to an extensive comparative dictionary of the three languages, even throwing in 9 Berber comparisons and 5 Latin ones at the end. He definitely hedges his bets on the cause of this obvious similarity between the three languages, but seems to come surprisingly close to the correct explanation – common descent – at times… something to bear in mind next time you read about Sir William Jones having founded comparative linguistics in 1798.
The post goes on to provide a quote from Yehudah, in both translation and Arabic transcription (it was originally in the Hebrew alphabet).
An earlier post, equally interesting, is on demonstratives in Semitic (are Hebrew ha- and Arabic al- really cognate?).