As is said in the Florilege of Hearing:
Through hearing, on will know the Dharmas; Through hearing, one will turn away from sin; Through hearing, one will forsake the meaningless; Through hearing, one will attain Nirvana.
Initially, to ascertain through hearing, [as is said] in a Sutra:
Listen intensely, well and memorize!
From The Sacred Words of Manjushri – Stages of the Path to Enlightenment by His Holiness the Fifth Dalai Lama, Lobsang Gyatso As translated in: The Interwoven Transmission of “The Swift Path” and “From the Mouth of Manjushri”, commentary by Khensur Kangyur Rinpoche, translation by Ilia Durovic. To be published (approx 2014) by Jamgon Editions. Download a partial, draft translation of Instructions from The Mouth of Manjushri here.