The Buddha reflects on the Dhamma after his enlightenment and is encouraged by Brahmā Sahampati to rely on the Dhamma.

Paṭhamauruvela sutta - Uruvelā (First)

Thus have I heard Once, the Blessed One was dwelling in Sāvatthi, in Jeta's Grove, Anāthapiṇḍika's park. There, the Blessed One addressed the bhikkhus: "Bhikkhus."

"Venerable sir," responded the bhikkhus to the Blessed One. The Blessed One then spoke:

"Once, bhikkhus, I was dwelling near Uruvelā, on the bank of the Nerañjarā River, at the foot of the Ajapāla banyan tree. There, having just attained enlightenment and being in solitude, a reflection arose in my mind: 'Indeed, living without respect and guidance results in suffering. What if I were to honor and rely upon an ascetic or a brahmin?'

It then occurred to me, bhikkhus: 'I should only rely on another ascetic or brahmin to complete what is lacking in my aggregate of virtue. However, I see no one in the world with its deities, Māras, Brahmās, its ascetics and brahmins, kings and commoners, who possesses virtue superior to my own, to whom I could look up for respect and guidance.

In the same way, I should only depend on another ascetic or brahmin to fulfill what is lacking in my collectedness aggregate. But, I see no one in the world who surpasses my own collectedness.

Likewise, to complete what is lacking in my wisdom aggregate, I would depend on another ascetic or brahmin. However, I see no one in the world who surpasses my own wisdom.

Furthermore, to complete what is lacking in my liberation aggregate, I would depend on another ascetic or brahmin. Yet, I see no one in the world who possesses liberation greater than mine.

Thus, I considered: 'Why not honor and depend on this Dhamma that I have fully realized?'

Then, bhikkhus, Brahmā Sahampati, perceiving the deliberations of my mind, as easily as a strong man might stretch out or withdraw his arm, appeared before me from the Brahma-world. Brahmā Sahampati, draping his outer robe over one shoulder, knelt on his right knee, placed his hands together towards me, and said: 'So it is, Blessed One, so it is, Well-Gone One. Just as the past Fully Enlightened Ones honored and depended on the Dhamma, and as future Fully Enlightened Ones will do, so too should you, currently the Blessed One, the Fully Enlightened One, honor and depend on the Dhamma.'

After speaking, Brahmā Sahampati continued:

'The Buddhas of the past, And those yet to arise, As well as the present Buddha, All dispellers of sorrow.
All have revered the true Dhamma, They lived, they live, and they will live [in future] thus; This is the nature of the Buddhas.
Therefore, those who desire their own benefit, Aspiring for excellence; Should revere the Dhamma, Following the Buddha's teachings.'

Having spoken these words, bhikkhus, Brahmā Sahampati paid homage to me, circumambulated me with his right side towards me, and then disappeared. Thereafter, recognizing Brahmā's request and what was appropriate for myself, I honored and relied upon the Dhamma that I had fully comprehended and lived accordingly. And as the Sangha was also endowed with excellence, respect grew within the Sangha."