Commentary for Leviticus 19:35

לא תעשו עול במשפט YE SHALL NOT DO UNRIGHTEOUSNESS IN משפט — If this has a reference to the execution of justice it would be redundant, for it has already been stated (v. 15) “Ye shall do no unrighteousness in judgment”. What, then is the meaning of משפט mentioned here? It refers to what is right in respect to measure of length, to weight and to measure of capacity. The use of the word משפט here teaches us, therefore, that one who has to do with measuring (in trade or commerce) is termed (is regarded as) “a judge” so that if he gives false measure he is like the judge who perverts justice and he is therefore called "an unjust person” (עַוָּל), hateful, detested, doomed to destruction, and an abomination (cf. Rashi v. 15). He brings about those five things which are mentioned in connection with the judge who perverts justice: he defiles the land, profanes the Name of the Lord, causes the Shechinah to depart from Israel's midst, Israel to fall by the sword and to be exiled from their land (Sifra, Kedoshim, Chapter 8 5).

לא תעשו עול במשפט במדה במשקל ובמשורה, seeing that the term אונאה, unfair dealings, also includes unfair business practices, the Torah issues a general prohibition concerning this addressed both to the locally born Jew and the recent convert, or stranger. The words used include measures for measuring liquids, dry matters, as well as the use of deceptive weights.

במדה, measures of length used to measure fields.