“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” (Proverbs 6:1-2).
Herod is a perfect instance of being ensnared by what he said: "...The daughter of Herodias...pleased Herod so much that he promised with an oath to give her whatever she asked" (Matthew 14:6,7). Herod was trapped by what he promised, and he regretted it later: "The king was distressed but because of his oaths and his dinner guests, he ordered that her request be granted..." (v.9). Because of a foolish oath made by a proud man, John lost his life. It would have been a far less sin if Herod had broken his promise.
We should not promise what we cannot deliver. The Bible covers every occasion for every age, and this verse surely applies to credit cards. It is too easy to pull out our credit card when we want something (mea culpa!). We are putting up security for ourselves every time we go beyond our means with an innocent looking piece of plastic, so it's best to cut it up and out if we are constantly tempted with this particular snare. And we surely are drowning when we borrow from one credit card to pay on another one!
Accumulating bills and obligations do control us so that, in our worry, we can serve neither God nor others. "...But the worries of this life, the deceitfulness of wealth and the desires for other things come in and choke the word, making it unfruitful" (Mark 4:19). It is wisdom to keep a rein on both finances and obligations before they get a reign on us. We can live and die entangled in the cares of this world because we haven't been prudent. We also bring reproach upon religion if we live and die in others' debt.
This verse also applies to appeals. Others ask us to do things for them that are beyond our time and means but, because we want them to like us, we have a difficult time saying no. It isn't fair to them or us to say yes, and then be resentful. In a way, we have been dishonest when we take on more than we can possibly do or pay.
As for thinking we are doing others a favor by always doing for them, to quote an oldie, it is far better to teach someone how to fish than to be constantly supplying the fish for him/her. We don't help others by making them dependent on us. Every age has its prodigals who would just as soon sit by and take everything you give. Prudence dictates just when we must quit pouring time and money down another's bottomless pit.
Does this mean we can never become surety, or bail, for another? "If he has done you any wrong or owes you anything, charge it to me...I will pay it back..." (Philemon 18,19). Martin Luther said of these verses: "Even as Christ did for us with God the Father, thus Paul also does for Onesimus with Philemon." Of course there will be instances when our help will be needed. What is condemned is entanglement to the point of incapacitation. "You were bought at a price; do not become slaves of men" (1 Corinthians 7:23).
Neither a borrower nor a lender be;
For loan oft loses both itself and friend.
Shakespeare, Hamlet, 1.3:75.