Venerable Nyanatiloka Mahathera cites the Word of the Buddha on the contemplation of feelings (Diga Nikaya 22):

But how does the disciple dwell in contemplation of the feelings?

In experiencing feelings, the disciple knows: “I have an agreeable feeling;” or: "I have a disagreeable feeling,” or: "I have an indifferent feeling;” or: “I have a worldly agreeable feeling,” or: “I have an unworldly agreeable feeling,” or: “I have a worldly disagreeable feeling,” or: “I have an unworldly disagreeable feeling,” or: “I have a worldly indifferent feeling,” or: “I have an unworldly indifferent feeling.”

Thus he dwells in contemplation of the feelings, either with regard to his own person, or to other persons, or to both. He beholds how the feelings arise; beholds how they pass away; beholds the arising and passing away of the feelings. “Feelings are there:” this clear awareness is present in him, to the extent necessary for knowledge and mindfulness; and he lives independent, unattached to anything in the world. Thus does the disciple dwell in contemplation of the feelings. (Nyanatiloka 1967, 64–65)

The word “feeling” here indicates how the mind is “disposed” when it encounters an object or experience. When a pleasant feeling arises, it may arouse greed and desire. An unpleasant feeling may arouse fear, hate, or aversion. Neutral feelings may arouse delusion.

The secret to this meditation exercise is to look at experience and cut off the root of unwholesome volition when it begins to arise and interact in feeling. If we just let the mind play in an uncontrolled manner, the defilements will exert a role in coloring experience.

If, however, through mindfulness, we watch an experience as it arises and as it passes away, we can catch unwanted kamma and defuse the attachment, aversion, or indifference. Through mindfulness we can turn the experience back into a bare mental event.

The secret is to learn to let the flow of events arise and dissolve without being subjectively involved. When the unwholesome root of feeling loses its hold on events, events lose their illusory sense of permanence and become part of the impermanent flux of the stream of events. With subjective feeling thus suppressed in connection with observation, there is no sense of a permanent ego interacting with events. This is what non-involvement means. It is the detachment necessary for right mindfulness. (For more details see Bhikkhu Bodhi 1984, 45-46)

Venerable Nyanatiloka comments :

The disciple understands that the expression “I feel” has no validity except as a conventional expression . . .; he understands that, in the absolute sense (paramattha), there are only feelings, and that there is no ego, no experiencer (sic) of the feelings. (Nyanatiloka 1967, 65)

Venerable Nyanaponika Mahathera in his Contemplation of Feeling explicates in more precise detail:

Feeling (vedana) is understood as the bare sensation experienced as pleasant, unpleasant (painful), or neutral (indifferent). It is distinguished from emotion, a more complex phenomena which arises from the basic feeling but adds to it various overlays of an evaluative, volitional, and cognitive character. Feeling in the Buddhist sense is the second of the five aggregates constituting what is conventionally called “a person.” The specific factors operative in emotion belong to the aggregate of mental formations (sankhara-khandha) the fourth aggregate. . . .

Feeling arises whenever there is the arising of three factors—sense-organ, object, and consciousness. The meeting of these three is called . . . sense-impression, contact, or impact (phassa). Sense-impression is a mental, not a physical event.

It is six-fold, as being conditioned either by one of the five physical senses or by the mind. This six-fold sense-impression is the chief condition for the corresponding six kinds of feeling borne of contact through the five physical senses and of mind contact.

In the formula of dependent origination (paticca-samuppada), this relationship is expressed by the line, “Sense-impression conditions feeling” (passa-paccaya-vedana). When emotions follow, they do so in accordance with the next link of dependent origination, “Feeling conditions craving.” (vedana-paccaya-tanha). . . .

Feeling is one of those mental factors (cetasika) common to all types of consciousness. In other words, every conscious experience has a feeling tone, pleasant, painful, or neutral. . . .

The subsequent emotional, practical, moral, or spiritual values attached to any particular feeling are determined by the associated mental factors belonging to the aggregate of mental formations. It is the quality of those other mental functions that makes the co-nascent feeling either good or bad, noble or low, kammic or non-kammic, mundane or supramundane.

Since feeling in its primary state simply registers the impact of the object, in itself it is quite devoid of any emotional bias. Only when volitional evaluations are admitted will there appear emotions such as desire and love, aversion and hate, anxiety and fear, as well as distorting views.

But these admixtures need not arise, as the emotions are not inseparable parts of the respective feelings. . . .

This shows that it is . . . possible to stop at the bare feeling and that this can be done intentionally with the help of mindfulness and self-restraint. . . .

Through actual experience, it can be confirmed that the ever-revolving round of dependent origination can be stopped at the stage of feeling, and that there is no inherent necessity for feeling to be followed by craving.

Here we encounter feeling as a key factor on the path of liberation and we can see why, in the Buddhist tradition, the contemplation of feeling has always been highly regarded as an effective aid on the path.

The contemplation of feeling is one or the Four Foundations of Mindfulness (satipatthana). As such it may be undertaken in the framework of that meditative practice, aiming at the growth of insight (vipassana).

It is, however, essential that this contemplation should also be remembered and applied in daily life whenever feelings are prone to turn to unwholesome emotions. . . . There will be many such occasions, provided the mind is alert and calm enough to notice the feelings clearly at their primary stage.

In the contemplation of feelings there should first be a mindful awareness of the feelings when they arise. One should clearly distinguish them as pleasant, unpleasant (painful), or neutral. There is no such thing as “mixed feelings.”

Mindfulness should be maintained throughout the short duration of a specific feeling, down into its cessation. If the vanishing point of feelings is repeatedly seen with increasing clarity, it will become much easier to forestall the emotions, thoughts, and volitions which normally follow them so rapidly and so often become habitually associated with them.

Pleasant feeling is habitually linked with enjoyment and desire; unpleasant feeling with aversion; neutral feeling with boredom and confusion—and also serving as a background for wrong views. But when bare attention is directed towards the arising and vanishing feelings, these polluting additives will be held at bay. (Nyanaponika 1983, 3–5)

References

Bodhi, Bhikkhu. 1984. The Noble Eightfold Path: The Way to the End of Suffering. Kandy: Buddhist Publication Society.

Ledi Sayadaw. 1977. The Noble Eightfold Path and its Factors Explained. Kandy: Buddhist Publication Society.

Nyanaponika Mahathera. 1983. Contemplation of Feelings. Kandy: Buddhist Publication Society.

Nyanatiloka Mahathera. 1967. The Word of the Buddha. Kandy: Buddhist Publication Society.

Related features from Buddhistdoor Global

A Humanitarian Action for Other Living Beings: Creating Space for Urban Biodiversity through Buddhist Gardening
On Being Mindful of the Body
A Moment with Dr. A. T. Ariyaratne