What is the essence of all sentient beings?

Why is the Buddha so compassionate, yet able to leisurely watch from the heavens as the sentient beings of the Sahā world suffer all kinds of distress? Can the Buddha bear to watch this?

When my mother passed away, I was right at the stage of the mirage contemplation (mārīci-vipassanā). Many years beforehand, I had already made preparations for how to face my mother's death. In my mind I kept pondering: what is my mother composed of? Does this person "my mother" truly exist? During the process of handling my mother's funeral arrangements, I observed each person's mind consciousness and manas, observing everyone's psychological state, and thus I realized the mirage barrier (mārīci-pass). Everyone appeared so empty and illusory in my mind; I went through everything like a walking corpse, even though I still felt deep sorrow inside.

Then, when the Buddha observes sentient beings with His immeasurable wisdom, what are sentient beings? The universe and the world, human affairs, matter and principle—what are they all? The physical bodies of sentient beings are particles of the four great elements; their mind consciousness is the seeds of consciousness. When the Buddha looks at sentient beings, there are no sentient beings, nor their affairs and principles. That is one point. Secondly, sentient beings have their own karmic conditions and karmic force for suffering; if the causes and conditions have not arrived, even rescue would be useless. One can only watch as sentient beings drift in the ocean of birth and death, bobbing up and down; only when the causes and conditions ripen can one reach out to save them.