My son, if you have put up security for your neighbor, if you have struck hands in pledge for another,
if you have been trapped by what you said, ensnared by the words of your mouth,
then do this, my son, to free yourself, since you have fallen into your neighbor’s hands: Go and humble yourself; press your plea with your neighbor! Proverbs 6:1-3
These verses have been abused over the years. “Putting up security for your neighbor” is foolishly loaning someone money that he/she may never be able to pay back. It’s the living-beyond-your-means mentality that Solomon is objecting to. But I also think that it relates to naivete on the part of the lender.
As we progress through Proverbs, these types of verses will appear. Does it mean it’s a sin to co-sign a loan for someone else? No, but it may not be wise either. The co-signer may end up paying the entire loan, and often does. It’s certainly something to consider as we mature as Christians.
Doing the unwise thing is not always sin; sometimes it’s just, well, unwise.