I. The Doublet
The story of Yisro (Jethro) approaching Moshe and the people of Israel (Ex. 18:1-12) is told as a doublet, i.e. the story seems to be repeated. This phenomenon is used throughout the Bible by source critics to posit that the text we have is a patchwork of previous texts. However, I was surprised to find this doublet noted not by biblical critics but by the sixteenth century Torah scholar R. Shlomo Ephraim of Lunshitz in his classic K'li Yakar commentary to the Torah.
The K'li Yakar divides the passage, more or less, into these two sections:
1. Ex. 18:1-6, 12:The K'li Yakar points out that in passage 1 the name Elokim is used (with one exception) while in passage 2 the name YKVK is used. Also, in passage 1 Yisro heard about all that God had done for Moshe and Israel, i.e. God's positive help. In passage 2 Yisro heard about what God had done to Pharaoh and Egypt, i.e. God's punishing and destroying. Notice also that in passage 1 Yisro hears the news before the travels to the Israelites while in passage 2 he only blesses God after seemingly hearing about the news for the first time from Moshe.
Now Jethro, the priest of Midian, Moses' father-in-law, heard of all that Elokim had done for Moses, and for Israel His people, how that YKVK had brought Israel out of Egypt. And Jethro, Moses' father-in-law, took Zipporah, Moses' wife, after he had sent her away, and her two sons; of whom the name of the one was Gershom; for he said: 'I have been a stranger in a strange land'; and the name of the other was Eliezer: 'for the Elokim of my father was my help, and delivered me from the sword of Pharaoh.' And Jethro, Moses' father-in-law, came with his sons and his wife unto Moses into the wilderness where he was encamped, at the mount of Elokim; and he said unto Moses: 'I thy father-in-law Jethro am coming unto thee, and thy wife, and her two sons with her.' And Jethro, Moses' father-in-law, took a burnt-offering and sacrifices for Elokim; and Aaron came, and all the elders of Israel, to eat bread with Moses' father-in-law before Elokim.
2. Ex. 18:7-11:
And Moses went out to meet his father-in-law, and bowed down and kissed him; and they asked each other of their welfare; and they came into the tent. And Moses told his father-in-law all that YKVK had done unto Pharaoh and to the Egyptians for Israel's sake, all the travail that had come upon them by the way, and how YKVK delivered them. And Jethro rejoiced for all the goodness which YKVK had done to Israel, in that He had delivered them out of the hand of the Egyptians. And Jethro said: 'Blessed be YKVK, who hath delivered you out of the hand of the Egyptians, and out of the hand of Pharaoh; who hath delivered the people from under the hand of the Egyptians. Now I know that YKVK is greater than all gods; yea, for that they dealt proudly against them.'
II. K'li Yakar
The K'li Yakar, certainly no source critic, proposes the following solution to this doublet. There was an ancient belief in two gods -- one of good and one of evil. Initially, in what we termed the first passage, Yisro had heard about God doing good for Israel and knew that He was at least the god of the good. Later, after hearing from Moshe about the "evil," i.e. punishment of the Egyptians, Yisro realized that God is the God of everything, not just the good. That is when he fully recognizes God's power and glory, and is when he fully blesses God and brings sacrifices to Him. The name Elokim is associated with the good that God did and YKVK with the "evil."
I find this difficult for two reasons. First, I am not entirely sure but my understanding is that the belief in two gods is Zoroastrianism and was a much later religion. I believe that the ancient Egyptian and Midianite religions worshipped many gods, and not just two. In fact, the K'li Yakar specifically refers to the Babylonian religion of the talmudic era, long after the episode with Yisro. Second, K'li Yakar's explanation of why the name Elokim is used for the good and YKVK for the bad seems to me to be strained. One would have thought that it would be the reverse -- YKVK, the name of mercy, for the good and Elokim, the name of judgment, for the bad. It is the opposite, the K'li Yakar explains, to show that the righteous can reverse the attribute of judgment and the wicked can reverse the attribute of mercy.
III. Other Explanations
The Netziv, in his Ha'amek Davar commentary, explains that the name Elokim refers to the strictness God utilized in avenging the wrongs done to the Israelites. He further explains the repetition in that Moshe told Yisro what he had not yet heard, the mercy involved in the plagues. Moshe told Yisro that the plagues were not only vengeance but also in order to make God's presence known and that the plagues affected Pharaoh more than the other Egyptians for this very purpose.
Cassuto states that the name Elokim is a general term that refers to a god that was universally acknowledged while YKVK refers to the specifically Israelite God. Elokim is used except where emphasizing the Israelite God or when Moshe speaks. Moshe merely told Yisro more details that impressed him even more.
IV. The Critics
I would have thought that source critics would have jumped all over this doublet, and attributed the mention of YKVK in verse 1 as a mere gloss from a different source. But they don't. The following is from John Durham, Word Biblical Commentary to Exodus, pp. 240-241:
This collection of motifs around a single and dominant figure gives Exod 18 a kind of unity lacking in most of the narratives of Exodus, or, for that matter, most of the tetrateuch. The commentators have generally accounted for this by assigning Exod 18 to a single source, E (so Beer, 94-95; Hyatt, 186; Noth, 146), or to E with a few notes from J (so Driver, 161-67; Davies, 147; Knight, 125).In other words, despite the clear opportunity here to divide the passage into two, the thematic unity is enough to convince leading commentators and source critics that this passage is not a doublet. I find this significant.