Question
I was wondering what the historic rabbinical interpretations for Joel 3:4 are?
I am especially interested in the historical understand of the "moon turning to blood"...
Answer
This verse has many deep meanings on many levels most of which I am not aware of.
On the simple Pshat level, the Metzudat David explains this is a metaphoric statement describing the horrors and Tzarot the world will go through before the great Day of Judgment [Yom Hashem Hagadol VeHanorah] and the future redemption; according to the above interpretation, the sun will remain a sun and the moon a moon.
[I apologize for the previous reply; I looked in the wrong place by mistake]