राजविद्या राजगुह्यं पवित्रमिदमुत्तमम्। प्रत्यक्षावगमं धर्म्यं सुसुखं कर्तुमव्ययम् ॥

rāja-vidyā rāja-guhyaṁ pavitram idam uttamam pratyakṣhāvagamaṁ dharmyaṁ su-sukhaṁ kartum avyayam

Kingly Science, kingly Secret, supreme Purifier, this; intuitional, according to righteousness, very easy to perform, imperishable.

In plain words: Krishna calls this teaching the king of all knowledge and the king of all secrets. It purifies more than anything else. A person can sense its truth directly. It fits with what is right, it is very easy to practice, and it never fades.