Deuteronomy 24:12
If he be a poor man, you shall not sleep with his pledge;
WEB
And if the man be poor, thou shalt not sleep with his pledge:
KJV
What Deuteronomy 24:12 means
It tells a lender who has taken a poor person's cloak as security for a loan to return it every evening, so the borrower always has something to sleep under.
This is one of a cluster of laws in Deuteronomy protecting people who have to borrow. In that world a poor person's outer cloak was also their blanket, the one thing that kept them warm at night. A lender could take it during the day as a guarantee that the debt would be paid, but the law says it has to be handed back before dark, every single night.
The point is a limit on what a creditor may do. Even with a legitimate claim, he cannot hold on to the one possession the borrower needs to survive the night. The verse ties this to the lender's own standing before God: giving the cloak back is counted as righteousness. Mercy toward the vulnerable is written into the law itself and treated as a measure of a just person.