Gemara: Rav Chisda and Rabba bar Rav Huna would sit in judgment all day. Their hearts were weakened (Rashi- they were upset that they did not study Torah that day). Rav Chiya bar Rav Midifti cited for them a baraita: "The nation stood upon Moshe from the morning to the evening" (Shemot 18:13). Could you imagine that Moshe sat in judgment the whole day? When would he be involved in Torah? Rather it teaches you that any judge who renders an absolutely true ruling even during one hour is considered by the Torah as if he partnered with Hashem in the creation of the world, as this pasuk says "… from morning to evening" and there it says "it was evening and it was morning…" (Bereishit 1:5).
Ein Ayah: The greatest desire that fills the heart of great, righteous people is to always be involved in service of the community, improving it to the maximum, which is the most complete service of Hashem. When such people (Rav Chisda and Rabba) found they could help the public through the judicial system, they did not want to refrain from this holy work for even a short amount of time. How could they turn their back on the community to work on self-improvement, as the latter is focused on the individual? Thus, they neglected taking care of their personal physical and spiritual needs (both can be included in weakening their hearts).
Rav Chiya agreed that improving the community is the highest level of activity. However, involvement in such service should not totally preclude one’s efforts for self-improvement. For one who is involved in communal needs, all of his life, attending to even his personal physical and spiritual needs, is actually serving the community as well, as it enables him to succeed in his future communal work.
All of Moshe’s life was dedicated to the needs of the nation, as is represented by the pasuk that the nation stood over him, i.e., was sustained by him. He is described as being involved in judging them from the morning to the evening, even though this included time he was working on self-improvement, because all his efforts were intended to promote his great communal work. He who desires the best for the community should not neglect his own improvement but should reach the level to realize that his own advancement enables more complete advancement of communal goals.
Work for the public is not measured quantitatively but qualitatively. An hour of activity with a spirit at rest and a healthy body can be more beneficial than constant activity in a manner that weakens the body and overly compromises the spirit. This is the way Hashem created the world – the whole is dependent on its parts, whose advancement is necessary for the success of the whole. Day and night form one unit even though the day includes greater opportunities to act significantly. It is night that allows one to rest and have the strength to act during the day, which makes it equal to the level of the day.
For this reason, one who judges ideally for one hour is one whose every activity, whether intense Torah study, maintaining his health, or perfecting his refinement and ethics, enables him to positively influence others in the fullest sense. Getting the parts of the world to work symbiotically is basic to creation, and those who promote this are thus like partners in creation. Since the foundation of a Torah-based legal system is to help society function ethically, being a judge is also a great contribution to perfecting the world that Hashem created. This partnership can be reached through a small amount of public work, when the rest of his work is sincerely dedicated to making himself fit to continue serving the public.