What is the meaning of "Rachok Mah she'Hayah"?
Rav Sadya Gaon: What was, is distant.
Rashi: The far matters that were in the initial creation.
Ibn Ezra #1, Metzudas David: What was, is very far (hard to attain).
Ibn Ezra #2: What was, is only far; it did not pass [from possibility to attain it]. One can search until he finds it.
Rashbam: A deep matter that was, e.g. Ma'ase Merkavah and Sefer Yetzirah, is very far from me. I cannot understand it.
Ri Kara: What was before creation of the world, it is far from me.
Rid: Chachmah, which was far from me, I did not attain it; it is still far.
Seforno: To illustrate what was in Ma'ase Bereishis is very far.
Why does it say "v'Amok Amok Mi Yimtza'enu"?
Rav Sadya Gaon: Something deep and far - who will attain it?!
Rashi: I may not think about what is above and below [this world], what was before and what will be after (Chagigah 11b).
Ibn Ezra #1: The future is very deep.
Ibn Ezra #2: Who will find what is very deep? This is like "Mayim Amukim Etzah v'Lev Ish v'Ish Tevunah Yidlenah" (Mishlei 20:5).
Rashbam: Who can find (understand) what is so deep with his great Chachmah?
Ri Kara: What is deep (high) above and deep below, i.e. what is above [this world] and below it, who will find it?
Rid: Chachmah is very deep. Who will find its place?
Seforno: Beriyah [from nothing] is a very deep matter - the act of a Worker without a substance.
Metzudas David: Even something of the present, if it is deep, one will not understand it - if so, who can find it?