Sāstra means that you cannot throw it away. Nobody has thrown Bhagavad-gītā at any time, anywhere, because it is perfect. Nobody has thrown Bible—because they are perfect in knowledge. Jijñāsitam adhītaṁ ca. Jijñāsitaṁ susampannam api te mahad-adbhutam (SB 1.5.3): "You have done wonderful work."
And kṛtavān bhārataṁ yas tvaṁ sarvārtha-paribṛṁhitam: "And you have created the great literature Mahābhārata, in which everything is there." Eh? Jijñāsitam adhītaṁ ca. "And not only simply you have inquired, but you have studied fully." There are many inquisitive persons, inquire so many things, but do not study. Reciprocation. There must be study and inquiry. Just like a nice scholar in the college, he inquires from the professor, at the same time studies. So the process of acquiring knowledge is to study and to inquire.
So here it is said, jijñāsitam adhītaṁ ca brahma. Brahman means the Supreme Absolute Truth. "You have inquired sufficiently . . ." Because he was spiritual master, Nārada, he knows how he was inquisitive. So, "You have inquired about the Supreme Absolute Truth." Jijñāsitam adhītaṁ ca yat tat sanātanam. Absolute Truth, sanātana means eternal. Absolute Truth is not relative.