Since it is generally the case that one will experience bewilderment at the time of death, this Liberation by Hearing is indispensable, whatever one’s degree of familiarity with [meditative] practices. In the case of those who have considerable familiarity with [meditative] experience, the recognition of the nature of reality can arise instantly, as soon as awareness separates from the material body. Therefore, it is essential to cultivate this experience [of reality] during one’s lifetime. Those who have been introduced to [the nature of] awareness, directly, and who have cultivated [this aspect of meditative experience] during their lifetime, will have the greatest ability during the intermediate state of the time of death when the inner radiance arises.
Additionally, those who during their lifetime emphasized meditation on the deity, according to the generation and perfection stages of the way of secret mantra, will have the greatest ability during the intermediate state of reality, when the visions of the Peaceful and Wrathful Deities arise.
Given the above, it is extremely important to train the mind particularly in this Liberation by Hearing, while one is alive. It should be embraced. It should be read aloud. It should be thoroughly comprehended. It should be taken to heart perfectly. It should be read aloud three times [a day], without fail. Its words and meaning should be so clearly impressed on the mind that, even were one to be pursued by a hundred assassins, its text and meaning would not be forgotten.
This being called the Great Liberation by Hearing, even those who have committed the five inexpiable crimes will attain liberation upon hearing [a recitation of its words]. Therefore, it should be read aloud in public places. It should be propagated. Since the awareness becomes many times clearer during the intermediate state, even if this teaching is sensed, as now, only once, and even if its meaning is not understood, it will be remembered at the time [of death], without a single word being forgotten. Therefore it should be read aloud across the pillows of all who are sick. It should be read aloud in the presence of all the bodies of the dead. It should be propagated, far and wide.
To met with this [teaching] is a great good fortune. Except for those who have gathered the accumulations [of merit and pristine cognition], and purified their obscurations, it is difficult to encounter. Yet, once it is heard, liberation can be achieved just by avoiding a mistaken view. Therefore it should be greatly cherished. It is the essence of all teachings.
The Tibetan Book of the Dead: First Complete Translation