The word distinction
(biqqō’rěṯ) is used only here in the Old Testament and is derived from the verb which means, to seek.
It may signify that punishment will be inflicted after an investigation. In Exodus 22:16–17, for example, if a man lies with a virgin who is not betrothed, he must either marry her or pay a dowry to her family. A similar payment may be in view here.
20 “If a man lies sexually with a woman who is a slave, assigned to another man and not yet ransomed or given her freedom, a distinction shall be made. They shall not be put to death, because she was not free;