In analyzing the relationship between the report Yitro received in Midyan (verse 1) and the account he heard from Moshe (verse 8), commentators offer various approaches which can be divided into two main categories:
Moshe shared new events about which Yitro had not yet heard. The variations of this approach differ in identifying what was new:
Moshe vs. the Nation
Yitro had previously heard reports of Moshe's personal success, but Moshe added how Hashem had aided the entire nation after their exodus from Egypt.
Syntax issues in verse 1 – Rashbam interprets leMoshe uleYisrael ammo to mean "for Moshe, acting on behalf of Israel his nation".2 Accordingly, verse 1 focuses exclusively on what God did for Moshe, in that He protected him from Paroh, enhanced his reputation, and enabled him to perform miracles on behalf of the nation.3
Deliverance from the "תְּלָאָה" of the journey and the internal structure of verse 8 – According to Rashbam, the tela'ah refers both to Paroh chasing them and to the lack of food and water, while the first half of the verse presumably speaks of the plagues in Egypt itself.
Overlap between the accounts – Rashbam is able to avoid having any overlap.
Names of God – Rashbam does not address this issue.
Reason for Moshe's additional report – Initially, Yitro, as Moshe's relative, was most concerned about Moshe's own fate. Moshe, though, being a self-effacing leader, was focused on the good of the nation, rather than his own personal glory.
Yitro's reaction – The first report was most significant for Yitro on the familial level, and it prompts him to bring Zipporah and her sons to Moshe in order to reunite the family. In contrast, Moshe's report was focused on the nation, leading Yitro to react on the religious and national levels, with the family receding into the background. See Purpose of Yitro's Visit. Yitro's words in 18:10 combine both reports, blessing Hashem for saving both Moshe (and Aharon) and the people. This explains the doubling of Hashem's "deliverance" (הִצִּיל) in 18:10.4
Egypt vs. En route
Yitro had heard what happened in Egypt; Moshe focused on what happened at Yam Suf and in the wilderness.
Syntax issues in verse 1 – Seforno explains the ki to mean "when." In his reading, the initial report described only the plagues and miracles which took place at the time of the Exodus.5
Deliverance from the "תְּלָאָה" of the journey and the internal structure of verse 8 – Seforno explains that tela'ah refers to the lack of food and water and the battle with Amalek,6 as opposed to the first half of the verse which speaks of the events of Yam Suf.
Overlap between the accounts – According to Seforno there is no overlap, and Moshe recounted later events of which Yitro had not previously heard.
Names of God – Seforno does not relate to this issue.
Chronology and the need for Moshe's additional report – Based on Seforno's comments regarding the altar in 18:12, it is likely that he thought that Chapter 18 is in its chronological place. If so, Yitro may have left Midyan to visit Moshe soon after hearing the reports of the plagues which brought about the Exodus, and before news of the later miracles reached Midyan. Thus the need for Moshe's update.
Yitro's reaction – In 18:11 Yitro acknowledges the greatness of Hashem, as reflected in the punishments of the Egyptians in Egypt and at Yam Suf (thus combining the two reports), and consequently converts (18:12).7
General vs. Details
Yitro had heard a general account while Moshe filled in the details.
Cassuto appears to combine this difference with the distinctions of Rashbam and Seforno discussed above.
Syntax issues in verse 1 – Cassuto interprets leMoshe uleYisrael ammo to mean "for Moshe, and for Israel his nation,"8 with Yitro being focused first and foremost on his relative's welfare. In verse 8, Moshe corrects Yitro's error by emphasizing that Hashem performed his miracles "for Israel's sake."9
Deliverance from the "תְּלָאָה" of the journey and the internal structure of verse 8 – According to Cassuto the tela'ah refers to Paroh chasing them, the lack of food and water, and the battle with Amalek, while the first half of the verse speaks of the miracles in Egypt itself.
Overlap between the accounts – Moshe repeats the general description which Yitro has already heard in order to fill in the particulars.
Names of God – The report which initially came to Yitro spoke of the actions of Elohim, using His generic name (while noting that the Israelites refer to Him as Hashem). The name of Hashem, the God of Israel, is used in Moshe's speech and when Yitro reflects Moshe's words. See Character Titles and א-להים for more on the usages of the different names of God.
Reason for Moshe's additional report – Moshe, as an intimately involved eyewitness, was able to share many details that Yitro had not previously heard.
Syntax issues in verse 1 – The ki means "that" and precedes the parenthetical clarification that the Exodus was the subject of the reports which had come to Yitro.
Deliverance from the "תְּלָאָה" of the journey and the internal structure of verse 8 – The tela'ah refers only to the events at Yam Suf, which are the exclusive subject of the entire verse.11 A major advantage of this approach is that vayatzilem ("delivered them") refers solely to salvation from an enemy, and is consistent with its standard Biblical meaning.12
Overlap between the accounts – According to this possibility there is no overlap whatsoever.
Names of God – The original report in verse 1 which comes via Gentiles utilizes the generic name of Elohim.13 As would be expected, in verse 8, Moshe employs the name of Hashem which reflects God's supremacy and his special relationship with Israel. For elaboration, see Character Titles.
Chronology and the need for Moshe's additional report – Assuming that Chapter 18 is in its chronological place, Yitro may have left Midyan to visit Moshe soon after hearing the reports of the plagues which brought about the Exodus, and before news of the later miracles reached Midyan. Thus the need for Moshe's update.
Yitro's reaction and the uniqueness of Yam Suf – According to this interpretation, Yitro's reaction fits Moshe's report perfectly. It is specifically Moshe's report about the miracles of Yam Suf which prompts Yitro's exhilaration and profession of faith, as this was the greatest of the miracles, and Hashem's glory at Yam Suf was apparent, not just to Israel, but to all of the nations of the world. That the splitting of the sea (even more than the Exodus) had such a profound impact, is similarly manifest in the fear of the neighboring countries described in the Song of Yam Suf (Shemot 15:14-16), and in the words of Rachav (Yehoshua 2:9-11).14 Thus, it is not coincidental that Yitro employs the same verb הציל in 18:9,10 which Moshe had used in 18:8,15 as all three verses are speaking of the same "deliverance" at Yam Suf.16
Moshe did not describe any new events, but his retelling was intended to transform Yitro's understanding of the events and Hashem's role in them. This position subdivides regarding the message Moshe wanted to convey:
Moshe repeated the news to bring Yitro closer to Hashem
Yitro heard it all – The Mekhilta DeRabbi Yishmael cites three different opinions regarding the content of the original report which Yitro heard in 18:1: the battle with Amalek, the giving of the Torah, and the splitting of the sea.17 It then combines all three possibilities in describing what Moshe recounted to Yitro in 18:8.18 In addition, the Mekhilta brings three additional opinions as to the identity of the "good" to which Yitro reacts in 18:9 – the manna, the well, and the land of Israel.19
Rashi's adaptation of the Mekhilta DeRabbi Yishmael – Rashi combines almost all of the various opinions found in the Mekhilta,20 in some cases transferring them from one clause to another so as to make them fit better with the simple sense of the verses.21
Deliverance from the "תְּלָאָה" of the journey and the internal structure of verse 8 – According to both the Mekhilta DeRabbi Yishmael and Rashi, tela'ah refers only to hostile encounters with the Egyptians and Amalek, and vayatzilem ("delivered them") refers solely to salvation from an enemy, matching its usual Biblical meaning.
Overlap between the accounts – There is significant overlap between the two accounts.
Names of God – This position does not relate to this distinction.
Yitro's reaction – According to R. Eliezer in the Mekhilta DeRabbi Yishmael, Yitro came in order to convert, and thus Moshe's second account only provided further encouragement.22 However, it is also possible that Yitro came for family purposes, and that Moshe's account is what convinced him to convert. See Purpose of Yitro's Visit.
Hashem is just
Yitro had heard of the punishments the Egyptians received, but did not understand the justice involved. Moshe explained how the Egyptians deserved these punishments.
Syntax issues in verse 1 – Since R. Yitzchak Karo thinks that 18:1 focuses on how Paroh and the Egyptians were punished, he is forced to say that leMoshe uleYisrael ammo means "because of Moshe and Israel,"23 and that ki means "when." In his reading, the Exodus is not the focus of the initial report, but only the time at which the Egyptians were punished.24
Deliverance from the "תְּלָאָה" of the journey and the internal structure of verse 8 – The tela'ah refers to the Egyptians pursuing the Israelites, and explains why Hashem punished the Egyptians. Similarly, the first part of the verse clarifies that the Egyptians were punished on account of what they did to the Israelite nation ("עַל אוֹדֹת יִשְׂרָאֵל").
Overlap between the accounts – There is significant overlap because Moshe is explaining that the punishments were not arbitrary, but rather "measure for measure".
Names of God – The Toledot Yitzchak does not address this issue.
Yitro's reaction – Yitro arrived at a greater appreciation of Hashem as a result of his new understanding of Divine justice.25
Hashem rules over both good and evil
Yitro had heard only of the good that Hashem did for the Children of Israel; Moshe told him also of the punishments inflicted on Paroh, emphasizing that Hashem controls both good and evil.
Overlap between the accounts – The accounts describe the same events but do not overlap, as each reported on the consequences for a different nation.
Names of God – The name Elohim (the name usually associated with the Divine attribute of justice) is used in 18:1 regarding the redemption of the Children of Israel, while the name of Hashem (the name related to the attribute of mercy) is employed in 18:8 to describe the punishment of the Egyptians. The purpose of this reversal is to underscore for the reader the same message which Yitro learned, that both justice and mercy emanate from one God and that there are not two separate powers ruling over different realms.27
Yitro's reaction – Only after hearing Moshe's report did Yitro come to the realization that there is only one God who controls all of the forces in the world.
Hashem is the only God
Yitro had heard that Hashem took the people out of Egypt, but assumed that the miracles in the wilderness were performed by other gods. Moshe corrected his misperception, pointing out that everything was done by Hashem, the only God.
Syntax issues in verse 1 – According to Malbim, the ki means "and that", and Yitro thought that Elohim performed the miracles of the manna and water, while Hashem was responsible for the Exodus. The difficulty with this approach is that one would have expected the Exodus to be mentioned before the manna and water.
Overlap between the accounts – The accounts overlap as Moshe needs to correct Yitro's error.
Names of God – Malbim explains that verse 1 utilizes both the name Elohim as well as the name of Hashem because Yitro attributed different miracles to different gods. In contrast, in verse 8, Moshe uses only the name of Hashem to clarify that all actions were performed by Hashem, the only God.
Yitro's reaction – As a result of Moshe's words, Yitro was convinced that Hashem is the only God, and he therefore converted.