There are some who argue that the Southern slaveholders were biblical literalists who looked at the “letter of the law,” while those who wanted to abolish slavery could only refer to the “spirit of the law.” They say that Christian abolitionists had to ignore specific words in the Bible concerning slavery in exchange for non-specific commands concerning concepts like love and freedom. Therefore, they insist, the abolitionists were guilty of ignoring the “plain meaning” of the Bible.
Alexander McLeod, in his popular book (eleven editions were printed), Negro Slavery Unjustifiable, directly challenged this view. McLeod says he wrote his argument to counter the “deceptive error”  of the slave owners’ biblical claims. He didn’t do this by appealing to love, freedom, or the “spirit,” but by quoting a specific commandment of God:
“Whoever steals a man and sells him, and anyone found in possession of him, shall be put to death.” – Exodus 21:16, ESV
This means, if Southern slaveholders would have specifically obeyed the letter of the law, anyone who kidnapped Africans and tried to sell them should have been arrested as soon as their ship came into port with its illegal cargo of human flesh, and any person who possessed that stolen person was also subject to arrest. According to Old Testament law, the penalty for manstealing was death.
Also, since Southerners defended their so-called “biblical” right to hold slaves, they should have also upheld the biblical command against kidnapping and selling people. If they were actually biblical literalists, Southern slavery would have been shut down immediately, but the slaveholders of the South “cherry-picked” the Scriptures. McCleod also pointed out this literal commandment from God:
“If a slave has taken refuge with you, do not hand them over to their master. Let them live among you wherever they like and in whatever town they choose. Do not oppress them.” – Deuteronomy 23:15-16, KJV.”
If the Southern slaveholder was actually following biblical law, their cities and homes would have had to become places of refuge for slaves. The Fugitive Slave Act, which was used to round up slaves who escaped from the South, would never be allowed under Old Testament law.
The Underground Railroad was set up by Bible-believing Christians (such as Charles Turner Torrey, who personally freed around 400 slaves) as a way to be obedient, not only to the non-specific commands to love our neighbor or set the captive free, but to a specific law from the Old Testament which commanded the Hebrews to protect runaway slaves from their masters.
Even if Leviticus 25:45-46 (for example) appears to permit the Hebrews to have slaves (it doesn’t), the slaves were never allowed to be taken, or held, against their will, therefore the slaveholders immediately broke the Old Testament law and abolitionists such as Andrew McLeod used the Bible to make it clear that the slaveholders were sinning.