A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
exo 18:1VISIT OF JETHRO. (Exo. 18:1-27)
Jethro . . . came . . . unto Moses, &c.--It is thought by many eminent commentators that this episode is inserted out of its chronological order, for it is described as occurring when the Israelites were "encamped at the mount of God." And yet they did not reach it till the third month after their departure from Egypt (Exo 19:1-2; compare Deu 1:6, Deu 1:9-15).
exo 18:6and thy wife, and her two sons--See Exo 4:20.
exo 18:7Moses went out to meet his father-in-law, &c.--Their salutations would be marked by all the warm and social greetings of Oriental friends (see on Exo 4:27) --the one going out to "meet" the other, the "obeisance," the "kiss" on each side of the head, the silent entrance into the tent for consultation; and their conversation ran in the strain that might have been expected of two pious men, rehearsing and listening to a narrative of the wonderful works and providence of God.
exo 18:12Jethro . . . took a burnt offering--This friendly interview was terminated by a solemn religious service--the burnt offerings were consumed on the altar, and the sacrifices were peace offerings, used in a feast of joy and gratitude at which Jethro, as priest of the true God, seems to have presided, and to which the chiefs of Israel were invited. This incident is in beautiful keeping with the character of the parties, and is well worthy of the imitation of Christian friends when they meet in the present day.
exo 18:13on the morrow . . . Moses sat to judge the people, &c.--We are here presented with a specimen of his daily morning occupations; and among the multifarious duties his divine legation imposed, it must be considered only a small portion of his official employments. He appears in this attitude as a type of Christ in His legislative and judicial characters.
the people stood by Moses from the morning unto the evening, &c.--Governors in the East seat themselves at the most public gate of their palace or the city, and there, amid a crowd of applicants, hear causes, receive petitions, redress grievances, and adjust the claims of contending parties.
exo 18:17Moses' father-in-law said unto him, The thing . . . is not good--not good either for Moses himself, for the maintenance of justice, or for the satisfaction and interests of the people. Jethro gave a prudent counsel as to the division of labor [Exo 18:21-22], and universal experience in the Church and State has attested the soundness and advantages of the principle.
exo 18:23If thou shalt do this thing, &c.--Jethro's counsel was given merely in the form of a suggestion; it was not to be adopted without the express sanction and approval of a better and higher Counsellor; and although we are not informed of it, there can be no doubt that Moses, before appointing subordinate magistrates, would ask the mind of God, as it is the duty and privilege of every Christian in like manner to supplicate the divine direction in all his ways.