Vimalakirti is quoted as saying “I am sick because sentient beings are sick.”
Manjusri asked, “Householder, whence came this sickness of yours? How long will it continue? […] How can it be alleviated?”
“Manjusri, my sickness comes from ignorance and the thirst for existence and it will last as long as do the sicknesses of all living beings. Were all living beings to be free from sickness, I also would not be sick. Why? Manjusri, for the bodhisattva, the world consists only of living beings, and sickness is inherent in living in the world. Were all living beings free of sickness, the bodhisattva also would be free of sickness.
For example, Manjusri, when the only son of a merchant is sick, both his parents become sick on account of the sickness of their son. And the parents will suffer as long as that only son does not recover from his sickness. Just so, Manjusri, the bodhisattva loves all living beings as if each were his only child. He becomes sick when they are sick and is cured when they are cured. You ask me, Manjusri, whence comes my sickness; the sicknesses of the bodhisattvas arise from great compassion.”
From The Holy Teaching of Vimalakīrti: A Mahāyāna Scripture. Translated by Robert Thurman (1976) from the Tibetan version.