The unsurpassed wondrous Dharma can only be apprehended by the mind, not conveyed in words

Intuitive realization is the personal realization by the manas, while verbal transmission is an explanation using the language of the mind consciousness. The unsurpassed wondrous dharma is the highest and most wonderful tathāgatagarbha dharma, which each person must personally realize and verify; the guidance and hints given by others through words can never substitute for one's own personal realization. Personal realization requires many causal conditions—precepts, meditation (samādhi), wisdom, and merit must all be complete—and one must have already raised a deep questioning doubt, able to abide in mindfulness of this very object and investigate it, with the practice reaching 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 upon the manas has not been done thoroughly, it cannot touch the manas. Therefore verbal transmission cannot replace the manas's deliberation (manana) and investigation, and ultimately one cannot attain personal realization. 

When the power of meditative concentration and investigation is not yet deep enough, one should focus on doing the practice and not listen to others' views, nor consult the Buddhist scriptures or others' theoretical knowledge, because these will obstruct personal realization. Such matters of cultivation are entirely one's own affairs: just as in eating, whoever eats gets full; in the Buddha-dharma, whoever investigates personally realizes it. Without investigation, there is no realization; a dharma merely heard is like something stolen—it does not belong to oneself. The state of meditative absorption (samādhi) can only be initiated by oneself, and wisdom arises from one's own mind. Studying the Tripiṭaka and the twelve divisions of the canon forever falls short of one's own awakening. 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. However it is spoken of, what is spoken is not He; there is nothing spoken and nothing shown, and whatever 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 about 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?