Mmm. I have a couple...

"Slavery takes hold of few, but many take hold of slavery."
- Lucius Annaeus Seneca
"Trust me that as I ignore all law to help the slave, so will I ignore it all to protect an enslaved woman."
- Susan B. Anthony
"No one is more enslaved than a slave who doesn't think they're enslaved. "
- Kate Beckinsale
"A woman who does not become the slave of just one man becomes the slave of all men."
- Jose Bergamin

Granted, these aren't 'classic', per say, but they are rather significant.