Katha-1-2-23-nāyamātmā

Sri Shankara’s Commentary (Bhashya) translated by S. Sitarama Sastri

Com.—This text says that though this âtman is hard to know, still he can certainly be known well by proper means. This âtman is not attainable by the study of many Vêdâs, or by intelligence, i.e., a retentive memory of the import of books, or by any amount of mere learning. By what then can he be attained is explained. That âtman (self) whom the neophyte seeks, by the same self, i.e., by the seeker, can the âtman be known. The meaning is that, of one who seeks only the âtman, being free from desire, the âtman is attained by the âtman alone. How it is attained is explained. To the man who seeks the âtman, the âtman reveals its real form, i.e., its own true nature.

Links
Various resources on the Kathopanishad
Upanishad Series – Katopanishad Commentary by Swami Chinmayananda