A more thorough explanation:

A commission of assize is a legal authorization given by the monarch to a person to hold court and try cases while the justices in eyre held court elsewhere. This allowed for justice to be served in different parts of the country.

For example, if a crime was committed in a certain area, a commission of assize would be issued to a person to hold court and try the case in that area. This meant that the trial could be held locally, rather than requiring the accused to travel to a central location.

The commission of assize gave the person the power to hear a case from beginning to end, but it did not create a permanent court. The jurisdiction of the judges rested entirely on the commissions which were issued for each circuit.

Overall, the commission of assize was an important tool for ensuring that justice was served throughout the country, and it helped to establish the legal system that we have today.