"Pass by evil talk with dignity..."

لاَ يَشْهَدُونَ الزُّورَ وَإِذَا مَرُّواْ بِاللَّغْوِ مَرُّواْ كِراماً
"And those who do not witness falsehood, and if they pass by some evil play or evil talk, they pass by it with dignity."
(Quran 25:72)

Commentary by Ibn Kathir:
(And those who do not bear witness to falsehood,) refers to giving false testimony, which means lying deliberately to someone else.
(and if they pass by some evil play or evil talk, they pass by it with dignity.) They do not attend where falsehood occurs, and if it so happens that they pass by it, they do not let it contaminate them in the slightest.