פירוש על במדבר 10:32

והיה הטוב ההוא AND IT SHALL BE THAT WHAT GOODNESS [THE LORD SHALL DO UNTO US, THE SAME WILL WE DO UNTO THEE] — What good did they actually bestow upon him (i.e. when did they redeem their promise)? They (our Sages) say: When the Israelites were parcelling out the Land the most fertile part of Jericho proved to extend over an area of 500 by 500 cubits; they left it unparcelled and said: He in whose portion of land the Sanctuary will be built shall take it as a substitute for giving up the land upon which the Temple was built. In the meantime, however, they gave it to the children of Jethro — to Jonadab the son of Rechab, [as it is said, (Judges 1:16) “And the children of the Kenite, Moses’ father-in-law, went up out of the city of the palm tree” (which is identical with Jericho; cf. Deuteronomy 34:3)] (Sifrei Bamidbar 81).

והיה כי תלך עמנו, "It will be when you come with us, etc." Why did the Torah repeat the word והיה before coming to the principal message in the verse? Besides, the entire verse seems superfluous as it contains essentially what Moses had offered Yitro already in verse 29? We will try and explain the verse both according to the view of Rabbi Eliezer Hamadoi and the view of Rabbi Joshua. According to the view of Rabbi Eliezer we must look at the word והיה as being simply a continuation of Moses' offer in verse 29 as follows: "Seeing that you have already become "our eyes," you will continue to be so when you decide to remain with us. You will most certainly not be viewed as a proselyte whose new-found enlightenment can hardly be expected to illuminate at a time when the sun of enlightenment shines all around, etc." According to the view of Rabbi Joshua, Moses merely urged Yitro to retain the stature he had acquired while on visit with the Jewish people.

A fertile area of Yericho. דושנה [means] fertile land.