A new proverb was posted on Erev Shabbos Vayigash in the Mishlei section.
A man who lacks wisdom makes a commitment to guarantee a loan for his friend.
This proverb speaks of the commitment to guarantee a loan as being the act of an unwise person. He is unwise because he has not given sufficient thought to the possibility that he is exposing himself to an unexpected debt.
The implication is that before making any kind of commitment a person needs to give careful consideration to the likelihood of his having to fulfill that commitment and the potential difficulty he may have in meeting that obligation.