The Davidic Ethic is the heart of the Noble Habitus, and is the most stereotypical part of the code. It boils down to a “magnanimous personality”, someone that is generous and forgiving to another, especially if that other person is weaker, or of a lower social status than the knight.
It’s is predicated on the idea that a knight must stand up for the weak against the forces of evil; and the strength of the knight shall always be in that service. No knight that is worth his oath of fealty treats the weak poorly, and indeed would be the target of other, more righteous knights should he be so. The concept of the Black Knight encapsulates this principle, as all knights rally around a banner to defeat their fallen, unforgivable brother.
This also might have been the origin of the courtesy which knights give to women generally, at least in stories, as historically women have had a lower social status, relatively speaking, then men, at least prior to the modern age. Although this isn’t true across the board, especially when it came to royalty in England in particular, with its history of indomitable queens, including the one that reigns currently, it was frequently the case, especially in continental Europe, and moreso in the lower nobility and commoner classes.
The strong must always be benevolent toward the weak, and protect them from the forces of evil or malevolence that exist outside their ability to handle. It is the duty of the strong, in fact, to use their shield to shield the weak before themselves, and their sword against those who would do them harm, even prior to protecting oneself. The Ethic, perhaps older than several other knightly traits at least in refinement thanks to the proliferation of Biblical stories, may be the ultimate origin of the heretofore mentioned Largesse expectation. In this case though, instead of an expectation of monetary charity, it is the willingness to put your own life on the line for those under your care.
The knight, being a caretaker of people both physically and monetarily, therefore earned his place as a leader in society, either of men in the battlefield, or of serfs and freedmen in his demesne. The Ethic provided the knight the moral tools to administer to his lands and the lands of those in his care, with reverence to the law and equal loyalty to his king, and those who were bound to him. This balance, and good maintenance of it, was critical to the knight maintaining power, or accumulating more. Treat your people poorly, and they were likely to rise up, and attack you or assassinate you in your home, castle or not, consequences be damned. After all, if you are killed by a mob, it’s unlikely you hadn’t earned the honour; although leaders of the mob may be tried and punished, it would be too damaging to the demesne to hang them all. Even a knight can be replaced relatively easily if the people yearn for better leadership. Fail to serve your king and pay your knight’s fee, and you may find yourself with the troops of neighboring knights at your doorstep, or worse, the king himself at the head of a host looking for your head.
Thus the knight was constrained by limitations placed upon him by the very power that granted him his station. Invested in this station would be further power over those he ruled over, tempered by the expectation of the Ethic. In most jurisdictions, the holder of a demesne was also holder of Justice, high, middle, and low, especially if the knight also held the title of Baron, as they often did. Knights serving a Baron might only be able to dispense with middle and low justice, or to arrest and bring to the Baronial Court for justice to be meted, but the power of arrest is in most cases, also the power to dispense punishment, especially if the person to be arrested fees, or resists.
These controls are now most often seen in the limits of power for people in positions where force is still permitted. Police officers and soldiers are given bounds of jurisdiction, and limits to when force can be employed. In today’s age, with courts divorced from the position of the leadership in an effort to separate powers, the accused are now brought before a magistrate, or other judicial officer, and tried before someone charged with giving justice impartially. So while knights today, insofar as they exist, no longer carry out those duties, they are instead diffused to other professions and offices in our society.