Comentario sobre Exodo 4:20

על החמור UPON “THE” ASS — the ass designated for this purpose: this was the ass which Abraham had saddled for the purpose of travelling to bind Isaac on Mount Moriah, and this, too, is the ass upon which King Messiah will once show himself in public, as it is said, (Zechariah 9:9) “[Behold, thy king cometh unto thee, …] lowly and riding upon an ass” (Pirkei DeRabbi Eliezer 31).

AND MOSES TOOK HIS WIFE AND HIS SONS. The intent thereof is like that of the verse, And the sons of Pallu: Eliab.²⁹²Numbers 26:8. It states “sons” in the plural, but mentions only one son. A similar case is here, as Ramban explains. At that time, he had only Gershom, as Scripture mentions,²⁹³Above, 2:22. and his wife became pregnant with Eliezer on the way [to Egypt] or in Egypt, if she went there.²⁹⁴See Ramban further in this verse.
It is possible that before the Divine communication came to him on the mountain of G-d,²⁹⁵Above 3:1. only Gershom had been born. Zipporah however was already pregnant [with Eliezer], and when he returned to Jether his father-in-law,²⁹¹Verse 18. she gave birth, but because the King’s business required haste,²⁹⁶I Samuel 21:9. Ramban evidently understands here the word “king” as referring to G-d. he did not circumcise him, nor did he give him a name. On the way when his mother circumcised him,²⁹⁷Verse 25. she did not give him a name, as Moses was met at that time by the angel.²⁹⁸Verse 24. And see Rashi: “and the angel sought, etc.” It was after he came to Egypt and saw that he was saved from all those who sought his life that he then called him Eliezer, for the G-d of my father was my help, and delivered me from the sword of Pharaoh.²⁹⁹Further, 18:4. Our Rabbis have also stated³⁰⁰Shemoth Rabbah 5:8. that the child that was circumcised [by Zipporah, as mentioned here in Verse 25], was Eliezer.

וירכיבם על החמור, to let them travel from the desert where Moses tended the sheep to Midian, i.e. to her father’s home.