What passages "praise" (your word) slavery (using the common meaning of 'slavery' to be involuntary slavery of humans by humans)?
Here's a useful article:
12 Bible Verses about Slavery in the New Testament.
You can see, quite clearly, that the writers of the New Testament were well aware of slavery in society, and that they had no particular objections to it. We can be sure that if they thought it evil, as we do, they would certainly have spoken out against it.
Instead, we have Ephesians 6, Colossians 3, Titus 2 and Timothy 6 calling on slaves to respect their masters, and to serve them with devotion. Not to rise up against them, not to run away, not to reassure them that the writes will do their best to free them - but to "obey those who are your masters on earth, not with external service, as those who merely please men, but with sincerity of heart, fearing the Lord".
We also have Corinthians 7, which says that you are to stay in the place in which you are put, and Colossians 4 calling on masters to treat their slaves fairly. This is a pro-slavery position - the master should be just and kind towards his slaves, and keep them well.
This article also has a good summary of the position of the Bible on slaves and slavery. It makes the excellent point that "This would have been a marvelous opportunity for Jesus to condemn the institution of slavery and its abuse of slaves. But he is not recorded of having taken it".
This is, of course, quite true.
If the writers had actually believed that slavery was evil, they would certainly have said so. The simple conclusion is they saw nothing wrong with it.
Also, I'm sure you won't be interested in reading
this article, but it does contain a useful little list, which I shall paste in here:
Ephesians 6:5:
Slaves, obey your earthly masters with respect and fear, and with sincerity of heart, just as you would obey Christ.”
Colossians 3:22 says,
Slaves, obey your earthly masters in everything; and do it, not only when their eye is on you and to curry their favor, but with sincerity of heart and reverence for the Lord.”
1 Timothy 6:1:
All who are under the yoke of slavery should consider their masters worthy of full respect, so that God’s name and our teaching may not be slandered.”
1 Peter 2:18:
Slaves, in reverent fear of God submit yourselves to your masters, not only to those who are good and considerate, but also to those who are harsh.”
Titus 2:9-10:
Teach slaves to be subject to their masters in everything, to try to please them, not to talk back to them, and not to steal from them, but to show that they can be fully trusted, so that in every way they will make the teaching about God our Savior attractive.”
Notice that
nowhere does the Bible say what you or I would want it to say: "Slaves, run away from your masters if you can do so safely! And masters, God and Jesus hate your slaveholding. You should free your slaves immediately".