From the Anapanasati Sutta ~ the Teaching on Mindfulness of Breathing ~ Majjhima Nikaya, translated by Bhikkhu Nyanamoli and Bhikkhu Bodhi
"...And how, bhikkhus, is mindfulness of breathing developed and cultivated, so that it is of great fruit and great benefit?
"Here a bhikkhu, gone to the forest, or to the root of a tree, or to an empty hut, sits down; having folded his legs crosswise, set his body erect, and established mindfulness in front of him, ever mindful he breathes in, ever mindful he breathes out..."
from the Dhammapada ~ Arahantavagga 98-99 ~ translated by Thanissaro Bhikkhu
"In village or wilds,
that place is delightful
where arahants dwell.
where the crowds don't delight,
those free from passion
for they're not searching
for sensual pleasures."
Arannika Sutta - the Wilderness Dweller - Anguttara Nikaya: 4.259, translated by Thanissaro Bhikkhu
"Endowed with four qualities, a monastic is fit to stay in isolated forest & wilderness dwellings. Which four? [He is endowed] with thoughts of renunciation, with thoughts of non-ill will, with thoughts of harmlessness, and he is a discerning person, not dull, not a driveller. Endowed with these four qualities, a monastic is fit to stay in isolated forest & wilderness dwellings."
The Jina Sutta - Old - Samyutta Nikaya 16.5, translated by Thanissaro Bhikkhu
"...Kassapa, what compelling reason do you see that you for a long time have lived in the wilderness and have extolled living in the wilderness... that you have kept your persistence aroused and have extolled having persistence aroused?"
"Lord, I see two compelling reasons that for a long time I have lived in the wilderness and have extolled living in the wilderness... that I have kept my persistence aroused and have extolled having persistence aroused: seeing a pleasant abiding for myself in the here & now, and feeling sympathy for later generations: 'Perhaps later generations will take it as an example: "It seems that the disciples of the Awakened One and those who awakened after him lived for a long time in the wilderness and extolled living in the wilderness; were almsgoers and extolled being almsgoers; wore cast off rags and extolled wearing cast off rags; wore only one set of the triple robe and extolled wearing only one set of the triple robe; were modest and extolled being modest; were content and extolled being content; were reclusive and extolled being reclusive; were unentangled and extolled being unentangled; kept their persistence aroused and extolled having persistence aroused."'"
"Good, Kassapa. Very good. It seems that you are one who practices for the happiness of many, out of compassion for the world, for the welfare, benefit, & happiness of beings human & divine. So continue wearing your robes of cast off hemp cloth, go for alms, and live in the wilderness."
Aranna Sutta ~ The Wilderness ~ Samyutta Nikaya 1.10, translated by John D Ireland
Thus have I heard. At one time the Lord was staying near Savatthi, at the Jeta Grove in Anathapindika's monastery. Now when night was passing a certain devataa, lighting up the whole Jeta Grove with her surpassing beauty, approached the Lord. Having drawn near and prostrated herself she stood to one side.
Standing there the devataa said:
Those living in the forest,
Peaceful and calm, of pure life,
Eating but one meal a day:
How is it they appear so radiant?
The Lord replied:
They sorrow not for what is past,
They have no longing for the future,
The present is sufficient for them:
Hence it is they appear so radiant.
By having longing for the future,
By sorrowing over what is past,
By this fools are withered up
As a cut down tender reed.