The Supreme Wonderful Dharma Can Only Be Understood by the Mind, Not Explained in Words

Understanding through tacit insight is the personal realization by the manas, while verbal transmission is the explanation in the language of the mind consciousness. The unsurpassed wondrous dharma is the highest and most wondrous tathāgatagarbha dharma, which each person must personally realize and verify; the guidance and hints given by others through language can never substitute for one's own personal realization. Personal realization requires many causal conditions: precepts, meditative concentration (samādhi), and wisdom, as well as merit, must all be complete; moreover, a deep questioning doubt must have arisen, so that one can investigate with constant mindfulness, bringing one's practice to the level of the manas—only then can one personally realize the wondrous dharma of the tathāgatagarbha. Verbal transmission can only first land in the mind consciousness; if the practice has not been carried to the manas, it cannot touch the manas. Therefore verbal transmission cannot substitute for the manas's deliberation (manasikāra/manana) and investigation, and ultimately one cannot attain personal realization. 

When the practice of meditative concentration and investigation is not yet deep enough, one should devote oneself single-mindedly to the practice, not listen to others' views, and not consult the Buddhist sutras or others' theoretical knowledge, because these will obstruct personal realization. Cultivation is entirely one's own affair: just as in eating, whoever eats becomes full, so in the Buddha-dharma, whoever investigates personally realizes it; without investigation there is no realization, and a dharma merely heard is like something stolen—it does not belong to oneself. The state of meditative absorption (samādhi) can only be brought forth by oneself, and wisdom arises from within one's own mind. Studying the Tripiṭaka and the twelve divisions of the canon can never compare with one's own enlightenment. A practitioner should be like a great man, courageous in practice, doing everything personally, and rejecting all opportunistic shortcuts. 

That the unsurpassed wondrous dharma cannot be transmitted in words has another layer of meaning: the tathāgatagarbha, this subtle and profound dharma, cannot be expressed in language. No matter how it is spoken, what is spoken is not He; there is nothing spoken and nothing shown, and what is pointed out is also not He. No matter what, He simply does not come forward, does not manifest, does not speak, does not act—low-key and selfless, and even without any "key." What is to be done with such a dharma? Only personal realization, personal verification, and personal awakening can reveal His true face. What is heard or seen is not it; no one can transmit this dharma through transmission. So do you still want to listen to others' instructions?