Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.

Benjamin Franklin (1706-1790) American statesman, scientist, philosopher, aphorist

Letter (1755-11-11) to Royal Governor Robert Hunter Morris, from the Pennsylvania Assembly
    (Source)

Also given as, "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" (cited in the Historical Review of Pennsylvania (1759)).

The actual "Reply to the Governor" letter, a response to Morris' rejection of the Assembly's proposals for frontier defense, was written by a committee of which Franklin was a member. He is usually credited as largely being the author, and he used this phrase subsequent to this.