The Sūtra Spoken by the Buddha on the Five Precepts for Upāsakas (Regarding the Precept Against Gross False Speech)

The Buddha addressed the bhikṣus, saying: "I have employed various methods to censure those who speak falsely and to praise those who do not speak falsely. Practitioners should not engage in false speech even in jest, let alone deliberately. How much more so should they avoid intentional falsehood! Among those who transgress this precept, if an upāsaka (or upāsikā) who has received the five precepts, without knowing or having attained the supramundane Dharma surpassing that of ordinary people, declares to others: 'I am an arhat,' 'I am one aspiring to arhatship,' 'I am an anāgāmin,' 'I am a sakṛdāgāmin,' 'I am a srota-āpanna,' 'I am one aspiring to srota-āpatti,' 'I have attained the first dhyāna,' 'I have attained the second dhyāna,' 'I have attained the third dhyāna,' 'I have attained the fourth dhyāna,' 'I have attained the four immeasurable minds of loving-kindness, compassion, sympathetic joy, and equanimity;'

'I have attained the formless absorptions: the sphere of infinite space, the sphere of infinite consciousness, the sphere of nothingness, the sphere of neither perception nor non-perception,' 'I have attained the contemplation on impurity,' 'I have mastered ānāpānasmṛti (mindfulness of breathing),' 'Devas come to where I am,' 'Nāgas, yakṣas, gandharvas, piśācas, kumbhāṇḍas, rākṣasas come to where I am,' 'They question me and I answer them,' 'I question them and they answer me'—all such declarations constitute a transgression that is non-repentable (āpatti apratikramaṇīya).

The above is the Buddha's teaching on the precept against false speech, primarily addressing major falsehoods (mahā-mṛṣāvāda), which concern untruths about profoundly significant matters; minor falsehoods are not discussed here. Regarding major matters, especially the actual realization of supramundane Dharma, one absolutely must not speak falsehoods or deceive others by falsely claiming to be a sage. The karmic retribution for impersonating a sage is extremely grave. Impersonating an earthly king would result in execution and public display of the head, with punishment extending to one's entire clan—how much more severe then is the offense of impersonating a sage, who far surpasses any worldly king! Such a transgression is non-repentable and will inevitably lead to rebirth in the lower realms. Therefore, everyone must be extremely cautious and meticulous regarding claims about supramundane Dharma. Unless one is absolutely certain and possesses irrefutable evidence, one must never casually spread claims of having attained any supramundane state. Regardless of who may have confirmed it, if the claim is untrue, one will certainly suffer severe karmic retribution. May all Buddhist practitioners be exceedingly cautious and avoid the offense of major false speech. Once this human life is lost, it is extremely difficult to regain it.

Why do so many people like to proclaim outwardly that they have attained this or that Dharma, or achieved this or that fruit? What is the psychology of sentient beings in this? Delving deeply, it is nothing more than a desire to prove oneself superior, to excel beyond others, to be better than others, to show that others are inferior; or to seek the respect, admiration, and reverence of others, to make others submit to oneself, to stand out from the crowd, and so forth—all stemming from self-conceit, narcissism, and arrogance. This is all based on the mind harboring both "self" and "others," with the mark of self fully present and the mark of others fully present. They have not eradicated the view of self (satkāyadṛṣṭi) and have not attained any Dharma; therefore, they remain ordinary beings fully possessed of the view of self. Those who wish to attain the Dharma of the sages must deeply investigate their own minds, excavate the "I" within their hearts, and destroy and eliminate it, not allowing that "I" to emerge again to confuse themselves and add afflictions, karmic obstacles, and suffering.