56.
The Discourse on the Internal Sense Bases as Suffering
223.
"The eye, monks, is suffering, etc.
The tongue is suffering, etc.
the mind is suffering.
Seeing thus, etc.
He understands: ... there is no more coming back to any state of being.'"
Ajjhattāyatanadukkha Sutta [SN 35.223, PTS 4.155]
Also known as: Ajjhattāyatanadukkhasuttaṃ