The Magna Carta is one of the most important documents in history. It is often considered the document that first limited the authority of the king in England.
However, the Magna Carta was mostly meant to protect the barons of England, not the commoners. Nevertheless, it did provide some protections for them as well.
For example, the Magna Carta established that no one, not even the king, can be above the rule of law. This is an important idea that allowed society to feel more equal. Moreover, it established legal concepts such as habeas corpus, which limits the arbitrary actions of the law. These concepts most likely made the commoners feel less abused and allowed them to think of the law as less arbitrary.