There are several I like, for example:

“The first duty of a revolutionary is to be educated.“ -Che Guevara

“The goal of socialism is communism.” - Lenin

“Workers of the world, unite” - Marx and Engels

“God is on your side? Is He a Conservative? The Devil’s on my side, he’s a good Communist.” - Stalin

“You can kill a revolutionary, but you can never kill the revolution” - Fred Hampton