Sam2
Yerushalmi Terumoth (ch. 1):
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Also, see Mesilat Yesharim (ch. 11) about the severity of this sin, where he brings this and other sources.
Found this on stack exchange.
I am not blaming anything on tznius all I’m saying is that looking at things you shouldn’t leads you to have shmutz in your head and it tends to come out of your mouth.