The letter Tsadhe [צ] symbolizes justice and righteousness in both man and God. In Hebrew, tṣadîq [צַדִּיק] is the word for righteous, and the very first word in this stanza of Psalm 119. A writer at Hebrew Today says a righteous man is “a person who safeguards and protects his eyes from evil things and protects his mouth and speech from saying bad things”.
That’s certainly part of it, though it leaves out the positive aspects of righteousness.