And Jethro, Moses' father in law, took a burnt offering and sacrifices for God: and Aaron came, and all the elders of Israel, to eat bread with Moses' father in law before God. Jethro - took a burnt-offering - עלה olah. Though it be true that in the patriarchal times we read of a burnt-offering, (see Genesis 22:2, etc)., yet we only read of one in the case of Isaac, and therefore, though this offering made by Jethro is not a decisive proof that the law relative to burnt-offerings, etc., had already been given, yet, taken with other circumstances in this account, it is a presumptive evidence that the meeting between Moses and Jethro took place after the erection of tabernacle. See Clarke's note on Exodus 18:5.
Sacrifices for God - זבחים zebachim, slain beasts, as the word generally signifies. We have already seen that sacrifices were instituted by God himself as soon as sin entered into our world; and we see that they were continued and regularly practiced among all the people who had the knowledge of the only true God, from that time until they became a legal establishment. Jethro, who was a priest, (Exodus 2:16), had a right to offer these sacrifices; nor can there be a doubt of his being a worshipper of the true God, for those Kenites, from whom the Rechabites came, were descended from him; 1 Chronicles 2:55. See also Jeremiah 35.
And Aaron came, and all the elders of Israel to eat bread - The burnt-offering was wholly consumed; every part was considered as the Lord's portion, and therefore it was entirely burnt up. The other sacrifices mentioned here were such that, after the blood had been poured out before God, the officers and assistants might feed on the flesh. Thus, in ancient times, contracts were made and covenants sealed; See Clarke's note on Genesis 15:13, etc. It is very likely, therefore, that the sacrifices offered on this occasion, were those on the flesh of which Aaron and the elders of Israel feasted with Jethro.
Before God - Before the tabernacle, where God dwelt; for it is supposed that the tabernacle was now erected. See Clarke's note on Exodus 18:5; and see Deuteronomy 12:5-7, and 1 Chronicles 29:21, 1 Chronicles 29:22, where the same form of speech, before the Lord, is used, and plainly refers to his manifested presence in the tabernacle.