"וַיֹּ֖אמֶר בִּ֣י אֲדֹנָ֑י שְֽׁלַֽח־נָ֖א בְּיַד־תִּשְׁלָֽח׃" (Exodus 4:13, Masoretic Hebrew)
My word-for-word translation of this is: "And he said 'Oh Lord, please send by the hand of (him who) you will send'" which matches the King James version pretty well: "And he said, my Lord, send, I pray thee, by the hand of him whom thou wilt send."
But NIV and other modern translations I've seen say this: 'But Moses said, “Pardon your servant, Lord. Please send someone else.”'
There seems to be a Hebrew idiom here, but I'm too inexperienced at Hebrew to understand how it works. Can someone explain the idiom to me? Or is this a difference in manuscripts that I missed?