Psalms 119:142

צִדְקָתְךָ צֶדֶק לְעוֹלָם וְתוֹרָתְךָ אֱמֶת

Your righteousness is an everlasting righteousness and Your Torah is truth.

The Shabbos afternoon prayer “Tzidkascha” is so called because it is made up of three verses, each of which starts with the word “tzidkascha” (Your righteousness). The ibn Ezra connects this verse conceptually to the previous verse, in which David says, “I am young and despised yet I have not forgotten Your laws.” The reason is because G-d’s laws reflect His eternal righteousness as well as the Torah’s eternal truth.