In the Words of the Rebbe:

"In that time... the only occupation of the entire world will be to know G-d exclusively. Israel will thus become great sages and will know the hidden matters and will grasp the knowledge of their Creator according to the capacity of man, as it says "for the earth will be filled with the knowledge of G-d as the waters cover the sea bed'".

- Dvar Malchus Parshas Shlach 5751