וַיֹּ֕אמֶר אַל־נָ֖א תַּעֲזֹ֣ב אֹתָ֑נוּ כִּ֣י ׀ עַל־כֵּ֣ן יָדַ֗עְתָּ חֲנֹתֵ֙נוּ֙ בַּמִּדְבָּ֔ר וְהָיִ֥יתָ לָּ֖נוּ לְעֵינָֽיִם׃
И сказал он: 'Не оставляй нас, я умоляю тебя; потому что ты знаешь, как нам расположиться в пустыне, и будешь нам вместо глаз.
Rashi
אל נא תעזב LEAVE [US] NOT, I PRAY THEE — The word נא is an expression of entreaty. Here it means: I beg of you, not to leave usin order that people should not say, “Jethro did not become a proselyte out of pure love for the Jewish faith. He believed that the proselytes, too, would have a portion in the Land; now, however, that he saw that they will have no portion in it he has deserted them and gone his own way (Sifrei Bamidbar 80).
Rashbam
כי על כן ידעת, while you have been with us in the desert you have become as indispensable as our eyes.
Sforno
אל נא תעזוב אותנו. At least allow your children to go with us,