Dutiyachaphassāyatanasutta
“Yo hi koci, bhikkhave, bhikkhu channaṁ phassāyatanānaṁ samudayañca atthaṅgamañca assādañca ādīnavañca nissaraṇañca yathābhūtaṁ nappajānāti. Avusitaṁ tena brahmacariyaṁ, ārakā so imasmā dhammavinayā”ti.
Six Fields of Contact (2nd)
“Mendicants, anyone who doesn’t truly understand the six fields of contact’s origin, disappearance, gratification, drawback, and escape has not completed the spiritual journey and is far from this teaching and training.”