The gemara in Shabbos (10a) states that one who properly and honestly judges a legal case is a partner to Hashem in the creation of the world. This is very great praise, but what does it mean?
The Ein Yaakov gives two answers. First, when two people come before a judge to litigate between them and to teach them the proper halachic resolution to a dispute in their lives, they are acknowledging a real, true belief that the Torah is min ha-shamayim and that its words are binding – and by extension, they are also expressing a belief in a number of other ikkarei emunah. By enabling this, the judge is, in effect, bringing Hashem into the world in a very real way, and he therefore can be considered to be a partner in the creation of the world.
A second answer is based on the mishnah at the end of the first perek of Avos that states that, in the absence of the Torah, avodah, and gemilus chassadim that are the purpose of the creation of the world as a result of the churban and galus and thereby the pillars upon which it is built, the world can be supported on a makeshift basis by justice, truth, and peace. (See the hakdama to the Ein Yaakov). Hence, the judge, as a purveyor of justice, is helping to maintain the world, and given that the world’s maintenance requires an individual ongoing act of creation at every moment, he is actually helping Hashem create the world at this moment.
The Maharal in Nesivos Olam (Nesiv HaDin, 1) explains why only one who engages in din can be considered a partner to Hashem, rather than, for example, one who engages in chesed. Although a person is commanded to walk in Hashem’s ways by doing acts of chesed (per Chazal, visiting the sick, clothing the naked, escorting a bride, burying the dead, etc.), it is impossible for a person to perfectly emulate the chesed of Hashem.
(R’ Shimon Shkop in his hakdama to Sha’arei Yosher makes a similar point by defining the kedusha (and perishus) of kedoshim tih’yu as altruism and doing things for others with no personal benefit. Hashem, who has no needs, can truly be considered to do everything for the needs of others. A human, though, who has personal needs, cannot physically ignore them completely in favor of the needs of others. Hence, although he is commanded to be a kadosh by going beyond himself and limiting his selfish actions to those that are his absolute needs, he cannot reach the absolute kedusha and perishus of Hashem, for whom there are no absolute needs and hence nothing but altruism.)
However, continues the Maharal, there are no degrees of mishpat and din. If something is a true verdict, it’s a true verdict, and if it’s not, it’s not. Hence, if one attempts to emulate the mishpat of Hashem, he becomes a complete partner, as there is no difference qualitatively between them.