Exodus 18:9

And Jethro rejoiced over all the good which the Lord had done unto Israel, and that He had given them manna, and the well, and that he had saved them from the hand of the Mizraee.

ויחד, a word derived from the category חדה, similar to the word חדוה in Chronicles I 16,27 עוז וחדוה, “strength and joy.” The construction follows the rule applicable to all roots of the ב,ג,ד,כ,פ,ת group of consonants (letters which sometimes take a dagesh chazak). They also lose their last root letter as a result of this. (in our verse the letter ה) More examples are the root בכה and the construction ויבך, vayevk, “he cried.” Another well known example is the root שבה, and the construction וישב, vayashav, “he returned.”

ויחד יתרו, he did not rejoice over the destruction of Egypt as a major power. This is what he should have done if he had been truly concerned with the honour and glory due to his Creator. We know this from Psalms 58,11. However, he did rejoice over the well being of the Israelites. He behaved like someone whose heart is moved by the tears of the oppressed.

ויחד יתרו, according to Rashi, the word ויחד means that Yitro’s flesh broke out in goose-pimples when reflecting on what had happened to Pharaoh and his army. Rashi’s grandson, Rabbeinu Tam, pointed out that Rashi had scriptural proof to support this interpretation. We find the following verse in Chronicles I, 2,35: ויתן ששן את בתו לירחע עבדו לאשה, “Sheshan gave his daughter to his (Egyptian slave) as a wife.” [This Egyptian slave had of course converted before being given a Jewish wife. Ed.] If you count from the word ירחע until the word אלישמע in the verses following the above until verse 41 you will get to Yishmael ben Netanya ben Elishama that there were 13 generations. Deduct 3 generations when Egyptians are not allowed to convert to Judaism and you will find confirmation for the opinion quoted by Rashi, that a convert’s genes do not completely disappear for 10 generations until there is not a trace of his original character that surfaces on occasion. Rashi, quoting a Mechilta, had warned that in the presence of a convert we must not speak in derogatory terms about a gentile unless being certain that the Jew to whom we speak who had had pagan ancestry, was already at least the descendant of nine previous Jewish generations. Yitro, a first generation convert, clearly would feel discomfort when reflecting on the fate that had befallen Pharaoh.