I realize now that my idea about Isaiah 50:4 is probably wrong and might be
the opposite of what the quote means. Maybe it is about the prophets having a
spirit of deep sleep on them (Isaiah 29:10-14), so they won't understand
visions, but Isaiah has a different situation.
Maybe it says "My L-rd, the L-rd, has given to me a tongue of learned ones.
For the knowledge to pervert is with a tired one (with being tired?), a word
He will arouse in the morning. In the morning, He will arouse to me an ear to
hear like the learned ones."
Maybe it means he will hear the word in the morning when he is not tired, so
he won't misunderstand it like the prophets who have a spirit of deep sleep
on them. Maybe they are the tired ones who pervert the knowledge they hear.
It is a wild guess, but I think it is interesting.