"I'm Spartacus!"
Crassus is asking for Spartacus to reveal himself, and if he does he will let the rest of the men and women go, but if he doesn't he will kill everyone. Antoninus steps in before Spartacus gives away his identity to protect him and says this famous line. Then everyone in Spartacus' army begins to claim that they are Spartacus as well. It's a symbol of unity amongst the people who were once slaves and have gained their freedom. They will not turn on each other and go back to the old way of thinking and being.
"Privately I believe in none of them - neither do you. Publicly, I believe in them all."
Gracchus says this to Julius Caesar after meeting with the Senate. His statement is one that strikes to the heart of the politician and government. That in public he is what he needs to be in order to maintain his relationships and thus his power, and he doesn't bring his personal convictions into the realm of government.
"Gladiators don't make friends. If we're ever matched in the arena together, I have to kill you."
Draba says this to Spartacus and the two do end up meeting in a Gladiator match for the pleasure of Crassus. But when Draba has the opportunity to kill Spartacus he does not do it. Instead he turns his weapons and himself on killing Crassus before he is slain by a guard's spear. Draba swore to never take another slave's life so long as he lives. And he keeps his promise.
