Yogācārabhūmi-śāstra, Volume 34 (46)

Original text:如是行者。于能随顺乐受诸行。及乐受中。由结缚行。趣入坏苦。于能随顺苦受诸行。及苦受中。由不可爱行。趣入苦苦。于能随顺不苦不乐受诸行。及不苦不乐受中。由不安隐行。趣入行苦。如是由结缚行。不可爱行。不安隐行增上力故。于三受中作如是说。诸所有受皆悉是苦。如是名为。由无常行作意。为先趣入苦行。

Explanation: Thus, the yogic practitioner, with regard to the formations that accord with pleasant feeling, and within pleasant feeling, by contemplating the characteristic of bondage, enters into the contemplation of the suffering of decay; with regard to the formations that accord with painful feeling, and within painful feeling, by contemplating the characteristic of the unlovely, enters into the contemplation of the suffering of suffering; with regard to the formations that accord with neither-painful-nor-pleasant feeling, and within neither-painful-nor-pleasant feeling, by contemplating the characteristic of insecurity, enters into the contemplation of the suffering of formations. In this way, owing to the power of intensified mental engagement (adhimātramanaskārabala) in contemplating the characteristics of bondage, the unlovely, and insecurity, the practitioner draws this conclusion regarding the three kinds of feeling: all feelings whatsoever are suffering. This is called taking the contemplation of the characteristic of impermanence as the initial mental engagement, for the purpose of first entering into the contemplation of the suffering of formations.