When Sarai is given the name Sarah, unlike Abram (who simply received the letter “heh”), Sarai loses the letter “yod” in her name, and it is replaced by the letter “heh.”
שָׂרַי -> שָׂרָה
Why? What could it mean?
The Midrash has an interesting quip about that.
“Why am I removed from the great woman of faith?” the little yod asks God. And to let him know that he was not forgotten, God placed the little yod on a future hero of faith: Joshua in Numbers 13:16.
These are the names of the men whom Moses sent to spy out the land; but Moses called Hoshea the son of Nun, Joshua.
Numbers 13:16 (NASB)
הוֹשֵׁעַ -> יְהוֹשֻׁעַ
This is why I love the Midrash so much.
Not because it provides definitive answers, but because it is the result of asking good questions.
Never stop asking questions.