Yogācārabhūmi-śāstra, Fascicle 34 (41)

Original text:云何复由别离行故。观无常性。谓依内外二种别离。应知诸行是无常性。依内别离无常性者。谓如有一先为他主。非奴非使。能自受用。能驱役他作诸事业。彼于后时退失主性。非奴使性。转得他奴。及所使性。于主性等。名为别离无常之性。

Explanation: How does one contemplate the impermanent nature through the practice of separation? Relying on the two kinds of separation, internal and external, one should know that all conditioned formations are impermanent in nature. The meaning of relying on internal separation to contemplate impermanence is this: suppose there is a person who was previously the master of others—not a slave, not an errand-runner—who could enjoy things at his own discretion and could direct others to carry out various undertakings. Later, this person no longer serves as a master; he loses the nature of a master, as well as the nature of not being a slave or errand-runner, and instead acquires the nature of being another's slave and errand-runner. Then, with respect to the nature of being a master and so forth, this is called the impermanent nature of separation.