משנה על פסחים 1:2

A jar of terumah which may have become impure:Rabbi Eliezer says: if it had been deposited in an exposed place, he must now place it in a hidden place; and if it had formerly been uncovered, it must now be covered. But Rabbi Joshua says: if it had been in a hidden place, he must now place it in an exposed place; and if it had formerly been covered up, he must now uncover it. Rabban Gamaliel says: let him not do anything new to it.