Or HaChaim on Numbers 10:31/אור החיים על במדבר י׳:ל״א

1 אל נא תעזב אותנו, "please do not abandon us, etc." According to Rabbi Eliezer Hamodai we must understand this verse as Moses asking Yitro not even to leave the Jewish people's camp temporarily. He alluded to this with the word נא. Regarding Yitro's argument that a light is quite superfluous during the time the sun shines, Moses did not accept that argument. He pointed out that Yitro's contribution to the Jewish people had already demonstrated that his presence was invaluable to them, i.e. ידעת חנותנו במדבר, i.e. when he told Moses to select heads of tens, etc. to help him judge the people he had proven that he had analysed the Israelites' problems in the desert correctly. Moses had demonstrated at that time that he accepted Yitro's advice thereby proving that Yitro's "light" could shine even while the moon or the sun were shining, i.e. while they enjoyed the Presence of the שכינה in their midst (Exodus 18,13-27).

2According to the view of Rabbi Joshua we must explain this verse as follows: The words אל נא תעזב mean that at this stage it was not appropriate for Yitro to depart. The reason it was inappropriate was that inasmuch as he was already familiar with the Jewish people's camp seeing their encampment was protected by G'd's cloud-and no one else knew their precise whereabouts-his knowledge was a security risk (compare Bamidbar Rabbah 19,20 in connection with Numbers 20,29 that Aaron had died). If he had never come to visit and had familiarised himself with the camp of the Israelites, Moses would not have minded his return to his homeland. According to the Midrash we referred to the whereabouts of the location of the camp of the Israelites remained a secret until the death of Aaron when the cloud enveloping the entire camp disappeared. Now that Yitro had been taken into G'd's confidence disappeared. Now that Yitro had been taken into G'd's confidence by knowing the whereabouts of the camp he should not depart. Another reason he should not leave was the fact that G'd had approved of the advice he had given to Moses and it had become part of the jurisprudence of the people. This is what he meant by describing Yitro as having become "the eyes of the Jewish people." If Yitro were to leave the Israelites after all this, this would be a desecration of the name of G'd. The Israelites would say that if a man who had participated in all their supernatural experiences and whom they had considered as on a high spiritual level could leave this could only prove that he had not been worthy to experience these miracles in the first place. Seeing that Yitro refused to remain, Moses expelled him from the proximity of the שכינה.