4.
The Discourse on Contact
325.
At Sāvatthī.
"Whatever desire and lust there is regarding eye-contact, monks, that is an impurity of the mind.
Whatever... there is regarding ear-contact...
whatever... there is regarding nose-contact...
whatever... there is regarding tongue-contact...
whatever... there is regarding body-contact...
whatever desire and lust there is regarding mind-contact, that is an impurity of the mind.
When, monks, for a monk... etc.
for phenomena to be realised by direct knowledge."
The fourth.