Exodus 18:6

And he said— The Vulgate renders it, mandavit ad Mosem: he sent persons to tell Moses. The word אמר amar is sometimes used in this sense, which is certainly just in this place; as it appears from the following verse, that Jethro and Moses had not yet met: it should therefore be rendered, and he sent to tell Moses; so the Arabic renders it. The Syriac has it, it was told Moses; and the LXX use the word ανηγγελη, which is of the same import.

Some, however, think, that Jethro wrote a letter to Moses, in which number is Sir Isaac Newton; who is further of opinion, that the use of letters was very early among the Midianites; and that Moses, "marrying the daughter of the prince of Midian, and dwelling with him forty years, there learned the art of writing." See his Chronology, p. 210.