In English, there exists no discrepancy in this statement; but read in Hebrew, the imperative is in the singular.
Rabbi Naftali Tzvi Yehudah Berlin (known as the Netziv) comments that the command is given in the singular because it is a warning to the people of Israel individually to ensure that each city has its own beit din. He continues to refer to the people as “Knesset Yisrael” – a term that encapsulates the entirety of the people of Israel and is always written in the singular. In contrast, at the birth of our nationhood, in Exodus, we are always referred to in the plural.
What has happened? Have we gone from being one nation when escaping Egypt, but now as we are awaiting to enter the land of Israel, we are commanded to behave as individuals? There is a striking feeling of “each man for himself” – yet that couldn’t possibly be true, especially if we can view the sojourn in the desert as a team-building exercise.
Moses and Aaron, the ultimate leadership team, faced a challenge in taking the people out of Egypt. They had been enslaved for over two centuries. A slave needs to always look out for number one. Every breath he takes is a precarious, his life hanging by a thread.
In order to convince the people that they were ready to leave Egypt, Moses and Aaron had to convince them not only in the omnipotent power of God, but also in their own strength, and that they had strength in numbers. And so the language needs to be in the inclusive and unifying plural.
But as we reach the end of our time in the desert, we have come together as one. The team-building has worked and we view ourselves as Knesset Yisrael, an holistic self-image that is more majestic than the sum of its individual parts.
The Torah isn’t asking an individual to set up judges for himself, but rather as a unified collective who recognises that the individual is the people and vice versa.