What does "Vayichad Yisro" mean?
Rashi #1, Seforno, Targum Onkelos and Targum Yonasan: And Yisro was glad. 1
Rashi #2 (from Sanhedrin 94a): It means that, when he heard of the downfall of the Egyptians, Yisro became covered with 'Chidudun Chidudin' (goose-pimples). 2
Hadar Zekenim (from Sanhedrin 94a): He put a sharp (Chad) sword on his flesh (circumcised, in order to receive Torah).
What was it that made Yisro happy?
Rashi: It was the news of the Manna, the well and the Torah, and above, the news of Yetzi'as Mitzrayim 1 that made him glad.
Seeing as up until then, no slave had ever succeeded in escaping from Egypt, and here 600,000 slaves had managed to leave (Rashi, citing the Mechilta). This Midrash evidently does not concur with the Midrash that 200,000 men of Efrayim left Egypt thirty years earlier (Refer to Shemos 13:17:2:5).
Out of compassion (Seforno).
Rashi writes that from Yisro's pain, we learn that one should not speak ill of a Nochri in the presence of a Ger up to 10 Doros. What is the source for 10?
Moshav Zekenim #1: Mitzrayim was No'ach's grandson (third generation). Avraham was 10 Doros from No'ach (the eighth from Mitzrayim), and Yisro was Avraham's grandson (Midyan's son 1 ), and still he was pained over Mitzrayim's fall. 2
Moshav Zekenim #2: Ten Doros refers to rows of folds due to old age. Until he dies, he is pained over disgrace to Nochrim, since he himself converted.
Da'as Zekenim, Hadar Zekenim, Moshav Zekenim citing R. Tam: Divrei ha'Yamim (1:2:35-41) lists 13 generations from Yircha until Elishama. The first three Doros of Egyptians 3 do not count, for they are not yet converts [who may marry into Yisrael]. The Pesikta says that this is Yishmael ben Netanyah, who killed Gedalyah. He was called Netanyah, because he was from the Nesinim, and he still did a Nochri act (murder). even though this was after 10 Doros.
Also R. Bechayei says that he was Midyan's son. This is difficult, for Bereishis 25:4 lists Midyan's sons, and none of Yisro's seven names (refer to 18:1:2:1) are among them! Also, Midyan was born before Avraham died (Bereishis 25:6). It is a Chidush to say that his granddaughter Tziporah was still single when Moshe came to Midyan more than 250 years later, and she gave birth to Eliezer 325 years later! (PF)
Moshav Zekenim: This is difficult, for we see righteous converts [surely they do not love their Nochri ancestors]!
Yircha was an "Eved Mitzri." Perhaps this is like R. Eliezer (Kidushin 3:13), who holds that there is an Eved Mamzer (If he is freed, he is a Mamzer), and likewise an Eved Mitzri. Or, it is like everyone. He was not a real Eved [Kena'ani], who is like a partial convert. Rather, he was a Mitzri, who was monetarily a slave. (PF)