See, for instance, SN 36.5, Datthabba Sutta(Nyanaponika, 1983).
In the Visuddhimagga 460, there is a similar but different threefold enumeration: wholesome (kusalā), unwholesome (akusalā) and indefinite (avyākatā) (Rhys Davids & Stede, 1921–25, ibid).
See, for example, the Chachakka Sutta (MN 148) which ascribes to the Buddha the following words:
"'The six classes of feeling should be known.' Thus was it said. In reference to what was it said? Dependent on the eye & forms there arises consciousness at the eye. The meeting of the three is contact. With contact as a requisite condition there is feeling. Dependent on the ear & sounds there arises consciousness at the ear. The meeting of the three is contact. With contact as a requisite condition there is feeling. Dependent on the nose & aromas there arises consciousness at the nose. The meeting of the three is contact. With contact as a requisite condition there is feeling. Dependent on the tongue & flavors there arises consciousness at the tongue. The meeting of the three is contact. With contact as a requisite condition there is feeling. Dependent on the body & tactile sensations there arises consciousness at the body. The meeting of the three is contact. With contact as a requisite condition there is feeling. Dependent on the intellect & ideas there arises consciousness at the intellect. The meeting of the three is contact. With contact as a requisite condition there is feeling. 'The six classes of feeling should be known.' Thus was it said...." (Thanissaro, 1998.)
For other references to the "six classes of feeling/sensation," see the Sattaṭṭhāna Sutta (SN 22.57) (Thanissaro, 1997b), and the Vedanā Sutta (SN 25.5) (Thanissaro, 2004).
Two virtually identical discourses that simply allude to the various number of vedana are MN 59 (Thanissaro, 2005b) and SN 36.19 (Thanissaro, 2005c). These different kinds of vedana are spelled out in SN 36.22 (Thanissaro, 2005a). See also Hamilton (2001), pp. 43-6.
Chachakka Sutta ("Six Sets of Six," MN 148). See for instance, the following statement attributed to the Buddha (trans. Thanissaro, 1998):
'Dependent on the eye & forms there arises consciousness at the eye. The meeting of the three is contact. With contact as a requisite condition, there arises what is felt either as pleasure, pain, or neither pleasure nor pain. If, when touched by a feeling of pleasure, one relishes it, welcomes it, or remains fastened to it, then one's passion-obsession gets obsessed. If, when touched by a feeling of pain, one sorrows, grieves, & laments, beats one's breast, becomes distraught, then one's resistance-obsession gets obsessed. If, when touched by a feeling of neither pleasure nor pain, one does not discern, as it actually is present, the origination, passing away, allure, drawback, or escape from that feeling, then one's ignorance-obsession gets obsessed....'
