Yogācārabhūmi Śāstra, Volume 34 (II)

Original text: 由四种行了苦谛相。谓无常行。苦行空行。无我行。由四种行了集谛相。谓因行集行。起行缘行。由四种行了灭谛相。谓灭行静行。妙行离行。由四种行了道谛相。谓道行如行。行行出行。如是名为了相作意。

Explanation: In cultivating the Four Noble Truths, one contemplates the mark of the truth of suffering through four contemplations: impermanence, suffering, emptiness, and non-self; one contemplates the mark of the truth of the origin of suffering through four contemplations: cause, origin, arising, and condition; one contemplates the mark of the truth of the cessation of suffering through four contemplations: cessation, tranquility, excellence, and relinquishment; and one contemplates the mark of the truth of the path through four contemplations: the path, rightness, practice, and emergence. Taken together, these dharmas are called the attention of discerning marks (ākāra-manaskāra).

This passage introduces the general content of cultivating the Four Noble Truths. The cultivation of each truth includes four contemplations, which together make sixteen contemplations, known as the sixteen contemplations of the Four Noble Truths.