In Paul's letter to Philemon, he is asking Philemon to free a slave in order to allow him to assist Paul in his ministry.  In this letter, Paul does not make an unequivocal statement against slavery, despite attempts by modern readers to argue that he does so.  However, Paul does show significant empathy for this slave, Onesimus.  And Paul tells us to "bless those who persecute you. Don’t curse them; pray that God will bless them. Be happy with those who are happy, and weep with those who weep."  Indeed, as believers are required to have unlimited, boundless empathy for all people.