This was said by the Blessed One, said by the Arahant, as I have heard:
“Bhikkhus, dwell delighting in |seclusion::solitude, privacy [paṭisallāna]|, enjoying seclusion, devoted to tranquility of mind, |not neglectful of meditation::meditating with diligence [anirākatajhāna]|, endowed with |discernment::clear seeing, penetrating internal vision [vipassanā]|, and practice in an |empty dwelling::uninhabited place, a physical home devoid of a self, e.g. a hut, a cave, forest [suññāgāra]|. For those bhikkhus who dwell delighting in seclusion, enjoying seclusion, devoted to tranquility of mind, not neglectful of meditation, endowed with discernment, and practice in an empty dwelling—one of two results is to be expected: either |final knowledge::spiritual insight [aññā]| [of full awakening] here and now, or, if there is any |residual clinging for existence::remnant of grasping for renewed becoming [upādisesa]|, the state of |non-returning::third stage of awakening where the five lower fetters of personal existence view, doubt, adherence to rules and observances, sensual desire, and ill-will are permanently dropped [anāgāmitā]|.”
The Blessed One spoke on this matter. In this regard, it is said:
Those with a calm mind, |discerning::astute, wise [nipaka]|,
|mindful::who has recollection, is aware, present [satimant]| meditators;
They rightly see deeply into the |ultimate reality::mental phenomena, mental qualities [dhamma]|,
unconcerned about sensual pleasures.
They delight in |diligence::quality of wishing to do one’s work or duty well, with alertness, carefulness and care [appamāda]| and are at peace,
seeing the danger in |negligence::carelessness, heedlessness [pamāda]|;
They are incapable of decline,
dwelling near to |Nibbāna::complete cooling, letting go of everything, deathless, freedom from calamity, the non-disintegrating [nibbāna]|.
This matter too was spoken by the Blessed One, as I have heard.