The Ethical Principle of Faithfulness

Trust
“Any city or house divided against itself cannot stand.” Matthew 12:25
Any human connection is based upon trust. This trust is not another acting in an ethical way, but acting in a predictable, reasonable way. If no one acts in a trustworthy manner, then human community cannot exist.

Faithfulness is keeping promises
But let your statement be, 'Yes, yes ' or 'No, no'; anything beyond these is of evil. Matt 5:38
If we make a verbal statement to act, it commits us to that act. To avoid the act, or to refuse to do the act is a violation of trust. If trust is violated, then community is broken down, and the trust will not readily be given again.

Faithfulness is loyalty
The LORD gives his own reward for doing good and for being loyal. (I Samuel 26:23)
Loyalty is to act in a socially responsible way to another in relationship. Primarily, it means that if we have a relationship with another, we will not violate that relationship by acting in a way that undermines the relationship, or that violates the trust of the other.

The action of loyalty is dependent on the relationship (e.g. I Peter 2)
Every relationship has it’s own social rules of loyalty, which are usually unspoken:
The loyalty of an employee is to do work for the employer. The loyalty of an employer is to provide for the employee. The loyalty of a spouse is sexual fidelity. The loyalty of a parent is to provide for the needs of the children. The loyalty of a citizen is to submit to the rulers. The loyalty of a ruler is to bring security. The loyalty of a friend is to assist in times of crisis

Small acts of faithlessness count
But I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart. Matt 5:28
If an act of disloyalty or unfaithfulness is small, it may seem to be insignificant—“It didn’t really hurt anyone.” However, small acts of disloyalty are an indication of the disloyalty that one holds within itself. That which is small will eventually display itself in something greater and more significant.

Faithfulness is acting in a trustworthy manner in accord with our word and with our relationship to others.

Can someone make a promise for someone else?
A person can only make a promise to the degree that they have the ability to control or be responsible for another’s actions. A parent can perhaps make a promise to a neighbor that her son would never break the neighbor’s windows again, if they are sure that they can control her son’s behavior. But the same parent cannot promise the judge ten years later that her son will be in court on time, because his behavior is out of her authority and ability to control. Freedom comes first.

Is anyone required to keep a promise for someone else?
Again, if one is responsible for another, then their loyalties become the one’s responsible loyalties. A parent is responsible for the actions of their son. But even family ties cannot ethically imply responsibility. An adult daughter should not be responsible for her father’s debts with her own money, nor the other way around. One may take responsibility for another’s commitments, but that would be a gracious gift, not a responsibility.

What if you are unable to keep a promise/retain loyalty?
More often than not, we place ourselves in circumstances in which we do not have the resources—either physical, mental, financial or otherwise—to keep a promise or to fulfill a loyalty. The best thing to do is to think through the circumstances ahead of time to see if you can actually keep the promise or the loyalty that you are committing to. Saying “no” is difficult when someone is asking you for a favor, but it is better than breaking your word and your trust.
If a promise must be broken, then the trust is broken and we must recognize that, admit it and take responsibility for it. Only on the basis of full repentance and forgiveness can trust be established again.

Are there promises implied without words?
Absolutely. Whenever we enter into a relationship, we make promises. When we hire someone, we promise to not abuse them or harm them. When we have a child, we promise to care for the child, the best we can. And if we ignore those implied promises, then we are prosecuted by the law, for the law recognizes those promises. If we have a friend, we imply that we won’t tell undermining stories about them. If we do gossip about them, then our friend will say, “I thought you were my friend?” Because the friendly actions we had toward them implied that we wouldn’t do anything to harm them.
This does not mean, though, that everyone has the same idea of what implied promises consist of. We may think that having a friend might also mean receiving calls at three in the morning. Well, it doesn’t imply that, but some may think it does. In this kind of case, we may have to reconsider our idea of what our relationship implies.