Did Buddha say "this is the Middle Way"?

What Lead to Conceive the Middle Way (or How This Was Conceived)

The middle way is avoid extremes in the form of asceticism and hedonism. The middle way was conceived based on based on the Buddha's experience of these extremes (asceticism and hedonism) when he realized this is not taking him to the final goal.

In chasing after sensual pleasure your moral virtue many perhaps laps. So there is a notion of virtue this puts some breaks on it.

Also you would chase after pleasures since your mind is not in your control and you are a slave to it. You overeat, chase after ladies and womanise, all because you are a slave of the mind. The Buddha mentioned to have master over the mind.

Also we fall into these extremes since we do not know reality as it is. We might think enjoy while you can or perhaps take the other extreme of austerity thinking through this you can get salvation. The Buddha taught that we develop wisdom of reality as it is so we do not fall into unconducive practices which do not give the expected results and outcome. Also lack of right understanding lead to attachment to various other view like creator God, Brahma is eternal, etc.¹ This is categorized as wisdom.

These 3 together forms the 3 main division of the middle path:

• Sila - morality
• Samadhi - mastery over the mind
• Panna - wisdom or to know things as they are

Morality is based on refraining from, delighting in, i.e., abstinence from any form any action which is harmful to oneself and others in terms of verbal action, physical conduct and may or earning your livelihood.

Mastery over the mind is to get control over the mind than it being wondering on its own. This control can be used to get sustained focus on any experiance (sometimes called absorption) which is feld so you can understand it better by closer scrutiny and analysis, i.e., right concentration. In order to do this you need be aware of what these experiences, i.e., right mindfulness. In order to realise this you have to apply effort to have the right mind states to foster development of concentration.

Ultimately this gives arise to the understanding on how the eradicate stress and suffering, i.e., Right View. With the propers understanding, your resolve is always conducive, i.e., Right Intention.

Where this was Conceived

This was formulated by the Buddha based on experience of his aesthetic practices and princely life before when he said realised it is futile to follow both paths.² Final realisation coming under the Bodhi Tree in Bodh Gaya on the day of enlightenment, i.e., following the middle path worked hence if was confirmed through direct experience. ³

Where was this 1st Preached and What Elaboration are Available

This was 1st preached in the Dhamma,cakka Pavattana Sutta as the middle way was preached in Sarnath. More detail elaboration of it is found in the (Magga) Vibhaṅga Sutta. Right view is one of the most important items as without it you will not take or walk the path. A detail elaboration of this is found in the: Samma,ditthi Sutta.

¹ See: An Introduction to the Brahma,jāla Sutta by Piya Tan and Brahma,jala Sutta.

²

...

But by these painful austerities, I did not attain any superhuman state, nor any distinction in knowledge and vision worthy of the noble ones. Could there be another path to awakening?’ Then, Aggi,vessana, I thought thus, ‘I recall that when my father the Sakya was occupied while I was sitting in the cool shade of a rose-apple tree, quite secluded from sensual pleasures, secluded from unwholesome states, I entered upon and abided in the first dhyana that is accompanied by initial application and sustained application, zest and joy born of seclusion. Could that be the path to awakening?’ Then following on that memory, Aggi,vessana, I realized, ‘That is the path to awakening!’ I thought thus, ‘Why do I fear the pleasure that has nothing to do with sensual pleasures and unwholesome states?’ I thought thus, ‘I do not fear the pleasure that has nothing to do with sensual pleasures and unwholesome states!’ I thought thus, Aggi,vessana, ‘It is not easy to attain that pleasure with a body so excessively emaciated. Suppose I ate some solid food—some boiled rice and gruel.’ And so, Aggi,vessana, I ate some solid food, boiled rice and gruel. Now at that time, Aggi,vessana, the five monks were waiting upon me, thinking, ‘If our recluse Gotama achieve some higher state, he will inform us.’ But when I ate the boiled rice and gruel, the five monks were disgusted and left me, thinking, ‘The recluse Gotama now lives luxuriously. He has given up the quest and reverted to luxury!’

...

Source: Maha Saccaka Sutta

³

...

When I knew and saw thus, my mind was liberated from the influx of sensual desire, from the influx of existence, and from the influx of ignorance. When it was liberated, there arose the knowledge: ‘It is liberated!’ I directly knew: ‘Destroyed is birth. The holy life has been live

...

Source: Maha Saccaka Sutta

According to Prajnaparamita tradition, here are the sutras where Buddha gave definition of the Middle Way:

SN 12.15 - Kaccayanagotta Sutta

"By & large, Kaccayana, this world is supported by (takes as its object) a polarity, that of existence & non-existence. But when one sees the origination of the world as it actually is with right discernment, 'non-existence' with reference to the world does not occur to one. When one sees the cessation of the world as it actually is with right discernment, 'existence' with reference to the world does not occur to one.

"By & large, Kaccayana, this world is in bondage to attachments, clingings (sustenances), & biases. But one such as this does not get involved with or cling to these attachments, clingings, fixations of awareness, biases, or obsessions; nor is he resolved on 'my self.' He has no uncertainty or doubt that just stress, when arising, is arising; stress, when passing away, is passing away. In this, his knowledge is independent of others. It's to this extent, Kaccayana, that there is right view.

"'Everything exists': That is one extreme. 'Everything doesn't exist': That is a second extreme. Avoiding these two extremes, the Tathagata teaches the Dhamma via the middle: From ignorance as a requisite condition come fabrications. From fabrications as a requisite condition comes consciousness. From consciousness as a requisite condition comes name-&-form. From name-&-form as a requisite condition come the six sense media. From the six sense media as a requisite condition comes contact. From contact as a requisite condition comes feeling. From feeling as a requisite condition comes craving. From craving as a requisite condition comes clinging/sustenance. From clinging/sustenance as a requisite condition comes becoming. From becoming as a requisite condition comes birth. From birth as a requisite condition, then aging & death, sorrow, lamentation, pain, distress, & despair come into play. Such is the origination of this entire mass of stress & suffering.

And here is what apparently is a more ancient version of the same sutra, from Samyukta Agama #301:

Thus have I heard. At one time, the Buddha was dwelling in the village of Nādika, at a residency deep within the forest. At that time, Kātyāyana Gotra approached the place of the Buddha. Bowing his head at the feet of the Buddha, he then withdrew to one side, and addressed the Buddha, saying: “Bhagavān, as the Bhagavān speaks of ‘right view,’ what is the right view? What does the Bhagavān establish as the right view?”

The Buddha told Kātyāyana Gotra, “The worldly have two kinds of support to which they grasp and adhere: existence and non-existence. This grasping and adhering is either supported by existence or supported by non-existence. Suppose one is without this grasping, not grasping at a mental realm which causes suffering, not dwelling, and not discerning a self. When suffering arises, it arises, and when suffering ends, it ends. He regards these without doubt and without confusion, and then without these, he has self-realization. This is called the right view, and what the Tathāgata establishes as the right view.

“Why is this so? One who sees arising in the world, is not one who holds to its non-existence. One who sees extinction in the world, is not one who holds to its existence. This is spoken of as ‘freedom from the Two Extremes,’ which is called the Middle Way. That is, that this existence is the cause of that existence, and this arising is the cause of that arising. These are caused by ignorance, including even the entire arising of the pure mass of suffering. When ignorance ends, then from this comes the end of such actions, including even the end of the pure mass of suffering.”

According to this, Buddha defined Middle Way as synonymous with Idappaccayatā (sanskr. idaṃpratyayatā).

Further, from SA 297/SN 12.35, The great discourse on the emptiness of dharmas:

“Regarding the statement conditioned by birth, aging-and-death arises, someone may ask: Who is it that ages-and-dies? To whom does aging-and-death belong?

“And he may answer: It is the self that ages-and-dies. Aging-and-death belongs to the self; aging-and-death is the self.

“To say that soul is the same thing as body, or to say that soul is one thing and body another, these have the same meaning, though they are expressed differently. For one who has the view which says that soul is the same thing as body, there is no point in the noble life. And for one who has the other view which says that soul is one thing and body another, there is also no point in the noble life. Following neither of these two extremes, the mind should move rightly toward the Middle Way.

From SA 300/SN 12.46:

The brahmin said to the Buddha: “What does this mean? When I ask, is the one who acts the one who experiences the result, you say that that is not to be declared; and when I ask is it that one acts and another experiences the result, you also say that that is not to be declared. What is the meaning of this?”

The Buddha said: “To declare that the one who acts is the one who experiences the result is to fall into the eternalist view. To declare that one acts and another experiences the result is to fall into the annihilationist view.

“Teaching the essence, teaching the dharma, I avoid these two extremes. Keeping to the Middle Way, I teach the dharma, namely: When this is, that is; this arising, that arises.

This was meant to be a comment, but it exceeded the word limit, so posted it as an answer.

The world (loke) is like a tar ball. You get stuck to it if you cling to it's sensual baits, and you still get stuck to it if you get into conflict with it. The middle path (this is not a statistically average way) is to see the tar ball's true nation, i.e. a volatile unpredictable place with repeated births and deaths, and let go of attachment to the world and any conflict towards the world. Practicing the middle path, one will become unbound from the tar ball.

Mr. Piya Tan's translation and commentary of the Kaccayanagotta Sutta (S 12.15) explains on what really is the middle way.

http://www.themindingcentre.org/dharmafarer/wp-content/uploads/2009/12/6.13-Kaccanagotta-S-s12.15-piya.pdf

In the Majjhima Nikaya, the Buddha gives his monks a discourse on the "The Exposition of Non-Conflict". In here he mentions the Middle Way:

"Here, bhikkhus, the Middle Way discovered by the Tathagata avoids both these extremes; giving vision, giving knowledge, it leads to peace, to direct knowledge, to enlightenment, to Nibbana. It is a state without suffering...and it is the right way. Therefore this is a state without conflict.

That is what the Blessed One said. The bhikkhus were satisfied and delighted in the Blessed One's words.

-- MN 139: Araṇavibhaṅga Sutta, p. 1085 - Bodhi, Trans.

In the Samyutta Nikaya, The Buddha also mentions the Middle Way. Here in the "The Book of the Six Sense Bases":

"There are, headman, these two extremes which should not be cultivated by one who has gone forth into homelessness: the pur­suit of sensual happiness in sensual pleasures, which is low, vul­gar, the way of worldlings, ignoble, unbeneficial; and the pursuit of self-mortification, which is painful, ignoble, unbeneficial.

Without veering towards either of these extremes, the Tathagata has awakened to the middle way, which gives rise to vision, which gives rise to knowledge, which leads to peace, to direct knowledge, to enlightenment, to Nibbana. And what is that mid­dle way awakened to by the Tathagata, which gives rise to vision . . . leads to Nibbana?

It is this Noble Eightfold Path; that is, right view . . . right concentration. This is that middle way awakened to by the Tathagata, which gives rise to vision, which gives rise to knowledge, which leads to peace, to direct knowledge, to enlightenment, to Nibbana.

-- Samyutta Nikaya: IV. The Book of the Six Sense Bases (Saḷāyatanavagga), p. 1350 - Bodhi, Trans.

In the Anguttara Nikaya, The Buddha mentions the Middle Way in relation to the practice of meditation:

“Bhikkhus, there are these three ways of practice. What three? The coarse way of practice, the blistering way of practice, and the middle way of practice".

“And what is the middle way of practice? Here, a bhikkhu dwells contemplating the body in the body, ardent, clearly comprehending, mindful, having removed longing and dejection in regard to the world. He dwells contemplating feelings in feelings . . . mind in mind . . . phenomena in phenomena, ardent, clearly comprehending, mindful, having removed longing and dejection in regard to the world. This is called the middle way of practice. “These, bhikkhus, are the three ways of practice.”

-- Anguttara Nikaya: The Book of the Threes: Ways of Practice, p. 372-373 - Bodhi, Trans.