This explanation is from Master Hsuan Hua‘s commentary on the Medicine Master Sūtra.

When the Buddha was about to enter Nirvāṇa, Ānanda was so overcome with grief that he could only cry. Although Ananda was a third-stage Arhat, he was still emotional. He couldn’t bear to think that the Buddha was going to enter Nirvana, so he wept piteously, forgetting about everything else.

Then another bhikṣu (Venerable Aniruddha) reminded him, “You’re in charge of remembering the Dharma spoken by the Buddha. The Buddha is about to enter Nirvāṇa, so you’d better think things over clearly. There are some important matters you should ask the Buddha about before he enters Nirvāṇa. All you know how to do is cry! What will become of us in the future?”

Hearing the Venerable One’s words, Ānanda collected his wits and said, “Yes, you’re right, but I’ve been crying so hard I can’t think straight. What should we ask the Buddha?”

The Venerable One said, “First of all, when we compile the sūtras in the future, how should they begin?”

Ananda replied, “Right! That’s very important.”

“Second, when the Buddha is in the world, we take the Buddha as our teacher. After the Buddha enters Nirvāṇa, whom should we take as our teacher?”

Ānanda said, “Yes, that’s also an important question.”

“Third, when the Buddha is in the world, all the bhikṣus dwell with the Buddha. After the Buddha enters Nirvāṇa, with whom should we dwell?”

“That’s certainly a good question.” Said Ānanda.

“Fourth, when the Buddha is in the world, he can subdue the evil-natured bhikṣus. After the Buddha enters Nirvana, who should discipline them?”

“These four questions are all extremely important,” said Ananda. “Now I will go and ask the Buddha.”

Then he went before the Buddha, knelt, placed his palms together, and said, “World-Honored One, since you are about to enter Nirvāṇa, there are some important questions I would like to ask. I hope the Buddha will compassionately answer them.”

The Buddha replied, “What are your questions? You may ask them now.”

“Buddha, you have spoken the Dharma for forty-nine years and expounded the sūtras in over three hundred assemblies,” said Ananda, “In the future, when we compile the sūtras, how should they begin?”

The Buddha told Ānanda, “Our sūtras are different from the scriptures of other religions, which begin by speaking of either existence or non-existence. You should begin the Buddhist sūtras with the four words, ‘Thus I have heard’ which means, ‘I, Ānanda, personally heard this Dharma, which is thus; it is not hearsay.”

Ananda said, “Okay, I will use the four words, “Thus I have heard.’ My second question is, when the Buddha is in the world, we bhikṣus take the Buddha as our teacher. Whom should we take as our teacher after the Buddha enters Nirvāṇa?”

The Buddha said, “After I enter Nirvāṇa, you bhikṣus should take the precepts as your teacher. The Pratimokṣa is your great teacher. If you uphold the precepts, it will be the same as when I am In the world. You should avoid all evil and practice all good deeds.” …

“Now I’ll ask the third question,” continued Ānanda. “When the Buddha is in the world, we dwell with the Buddha. We always live and study with the Buddha. After the Buddha enters Nirvāṇa, with whom should the bhikṣus dwell?”

The Buddha answered, “After I enter Nirvāṇa, all the bhikṣus should dwell in the Four Applications of Mindfulness.”

The Four Applications of Mindfulness

1. Contemplating the body as impure.
2. Contemplating feelings as suffering.
3. Contemplating thoughts as impermanent.
4. Contemplating dharmas as being without self.

The first application of mindfulness is to contemplate the body as impure. “But,” you say, “I take a bath and keep my body clean every day, and I put on makeup and jewelry to make it beautiful.” You may adorn your body with expensive jewelry and designer clothes, but it’s just like decorating a toilet; no matter how beautiful the toilet looks, it will still stink. …

Second, contemplate feelings as suffering. Feelings refer to sensations. No matter how enjoyable the sensation is, it is basically suffering. Happiness is the cause of suffering.

Third, contemplate thoughts as impermanent. Thoughts arise in continuous succession, one after another; they don’t last.

Fourth, contemplate dharmas as being without self. All dharmas (phenomena) are free of the notion of “me and mine.”

These are the Four Applications of Mindfulness. …

“Here is my fourth question,” said Ānanda. “When the Buddha is in the world, the Buddha can subdue the recalcitrant bhikṣus. After the Buddha enters Nirvāṇa, how should we deal with them?”

The Buddha said, “When you encounter a recalcitrant bhikṣu, just ignore him – don’t talk to him.” To ignore him is a passive way of expelling him. If no one pays attention to him or argues with him, he will soon grow bored of making trouble. If you pay attention to him or try to fight with him, he will think that he is getting somewhere. But if you ignore him, he won’t be able to do anything.  …

Recalcitrant bhikṣus are perverse and unreasonable. The more you argue with them, the more they enjoy it. That’s why the Buddha instructed us to ignore them.

The Three Doubts of the Assembly

When Ananda first ascended the Dharma seat – the seat where the Buddha spoke the Dharma – to begin the compilation of sūtras, there were many auspicious portents. For instance, Ananda became endowed with the thirty-two features and eighty subtle characteristics of a Buddha. Seeing those portents, the members of the assembly immediately had three kinds of doubts:

1. They thought that Ananda was their teacher, Śākyamuni Buddha, who had come back to life.
2. They thought that Ananda was a Buddha from another world. “Is this a Buddha who has come from another world to speak the Dharma in the Sahā world? Otherwise, why would he look like that?”
3. They thought Ānanda himself had become a Buddha.

The entire assembly was startled and at a loss, but once Ānanda said, “Thus I have heard,” their three doubts were dispelled. He was in effect stating, “This is the Dharma that I, Ānanda, personally heard Śākyamuni Buddha speak.”

Even the Arhats had three doubts when they saw Ānanda leading the compilation of the sūtras. As we listen to this sūtra, we may have a thousand or even ten thousand doubts. “Is this sūtra true? Did the Buddha really say this? What proof is there?” Our human brain starts plugging away, generating millions of doubts. So, you see, studying the Buddha-dharma is not that easy. Why haven’t we had any attainment? Too many doubts, that’s why!

A cultivator should take care not to doubt.
Once you doubt, you go astray

This quote is from Master Hsuan Hua‘s commentary on the Medicine Master Sūtra.

[Medicine Master’s Vaiḍūrya] Buddhaland has always been completely pure. It is always clean, pure, and undefiled, as bright and clear as vaiḍūrya.

There are no women in the Vaiḍūrya Land. Some women’s rights activists object to Amitabha Buddha’s Land of Ultimate Bliss, saying, “Why are there no women in that land? Does Amitabha Buddha look down on women? Does he favor men over women?” Not at all. We should realize that the Sahā world, in which men and women engage in lust, is filled with all kinds of evil and suffering. There is nothing worthwhile here. Everything is unclean.

The Sahā world Is known as the World of the Five Turbidities. Our time is very impure–that’s the turbidity of the eon. The things we see with our eyes are also unclean–that’s the turbidity of views. We all have incredibly many afflictions–that’s the turbidity of afflictions. Living beings are all born from emotional desire, and they are differentiated into males and females–that’s the turbidity of living beings. Not only human beings, but all beings with blood and breath are this way–born from sexual desire and dying from sexual desire. Even germs are imperceptibly brought into existence by this kind of desire. As long as there is desire, one is impure. The turbidity of life comes about because beings in the Sahā world live in an extremely unclean environment. The things we see, hear, smell, taste, touch, and think about are all unclean. Thus, this is known as the Evil World of the Five Turbidities.

In contrast to our dusty, defiled world, there is no dirt in the heavens; nor in the Western Land of Ultimate Bliss, where the ground is paved with gold; nor in the Eastern Vaiḍūrya Land, which has ground made of vaiḍūrya.

The people in the land of Ultimate Bliss are born transformationally from the vows of Amitabha Buddha, and they are free of desire. The Vaiḍūrya Land is created from the vows of Medicine Master Buddha. Because these Buddha lands are completely free of desire and birth occurs by transformation, not by sexual reproduction, there are no women in these lands.

No lower destinies and no sounds of suffering. The hells, hungry ghosts, and animals do not exist in the Vaiḍūrya Land. There aren’t any heartbreaking sounds of pain, sorrow, or distress.

This quote is from Master Hsuan Hua‘s commentary on the Medicine Master Sūtra.

We were born from ignorance. Ignorance is the root of birth and death, the source of all troubles and afflictions. The goal of our practice is to break through ignorance. Ignorance confuses us, so that we live as if drunk or dreaming, driven by the desires for wealth, sex, fame, food, and sleep. Ignorance causes us a lot of trouble. Once there is ignorance, it manifests in activity. We act on what we don’t understand, and then we become attached to appearances. When consciousness arises and begins to make distinctions, the marks of self, others, living beings, and a life span appear. Activity and consciousness generate name and form, making it possible to talk about things. Then the whole body comes into being, and with it, the six entrances (eyes, ears, nose, tongue, body, and mind). The six entrances come into contact with the external environment, and that contact brings on feeling. We differentiate between good and bad sensations, trying to avoid unpleasant sensations while craving pleasant ones. Thus, feeling then brings on craving. As we grasp at the object of our craving, there is becoming, then birth into the next life, and then old age and death all over again. The Twelve Links of Conditioned Causation describe the endless rounds of rebirth that all living beings undergo.

Pratyekabuddhas feel that this cycle is a lot of suffering, so they practice the Path in order to liberate themselves from birth and death. When they succeed, they attain to the fruition and become Pratyekabuddhas or Solitary Enlightened Ones, who belong to the Two Vehicles.

The Two Vehicles consist of the Hearers and Those Enlightened to Conditions (also called Solitary Enlightened Ones). The term “vehicle” is used to designate a class of cultivators. The practice of the Two Vehicles is not ultimate, because they have ended only physical birth and death, not the birth and death of thoughts. This is why Medicine Master Buddha vowed to lead the cultivators of the Lesser Vehicle to abide in the Great Vehicle and to resolve their minds on realizing the Buddhas’ Unsurpassed Enlightenment.