“Moses called Hoshea son of Nun, Joshua [Yehoshua]” (Numbers 13:16). What did Moses see that led him to add a yod to Joshua’s name? It is, rather, that Caleb took his reward from the Land, as it is stated: “Surely, the land on which your foot trod will be an inheritance for you and for your children forever” (Joshua 14:9), and Joshua took the reward of the ten men who constituted the spies, as an extra yod was added to him; yod equals ten. “Moses called Hoshea son of Nun, Joshua.” Alternatively, when Moses saw them, that they were wicked, he said to Joshua [Yehoshua]: “May the Lord deliver you [ya yoshiakha] from this generation.
Why Moses Changed Hoshea's Name to Joshua
Bamidbar Rabbah 16:9