The slave trade

9 We also know that the law is made not for the righteous but for lawbreakers and rebels, the ungodly and sinful, the unholy and irreligious, for those who kill their fathers or mothers, for murderers, 10 for the sexually immoral, for homosexuals, for slave-traders and liars and perjurers—and for whatever else is contrary to the sound doctrine (1 Tim 1:9-10).

In this passage, Paul condemns the slave trade. Marshall defines this as a "slave dealer, kidnapper."

Towner says this "denotes those engaged in the business of kidnapping or stealing people and selling them into slavery." He also says "the list describes extreme lawbreakers." 

Johnson says the term "has the specific sense of 'selling into slavery' free men who are captured in war. It can also be used for a kidnapper." 

He adds: "it almost appears as though Paul wanted to cite the most extreme examples of lawlessness he could find in each category."  

It was audacious for Paul to include this in his vice-list, considering the fact that the slave trade was integral to the Roman economic system. The statement borders on sedition.

It would be difficult to maintain the system without a fresh supply of slaves. Turn off the spigot and the stream dries up. 

Moreover, even if the system could sustain itself by second-, third-generation slaves, if Paul condemns the source, that casts a pall over the product as well as the process. 

This takes its place alongside Rev 18, which also condemns a slave-based economic system. Critics who say the Bible condones slavery overlook these passages.