Yogācārabhūmi-śāstra: Volume 34, Part 2

The characteristics of the truth of suffering are comprehended through four aspects: the aspect of impermanence, the aspect of suffering, the aspect of emptiness, and the aspect of non-self. The characteristics of the truth of the origin [of suffering] are comprehended through four aspects: the aspect of cause, the aspect of accumulation, the aspect of arising, and the aspect of condition. The characteristics of the truth of cessation [of suffering] are comprehended through four aspects: the aspect of cessation, the aspect of tranquility, the aspect of sublimity, and the aspect of liberation. The characteristics of the truth of the path [to cessation] are comprehended through four aspects: the aspect of the path, the aspect of fitness, the aspect of accomplishment, and the aspect of deliverance. This is called the comprehension of characteristics.

Explanation: When cultivating the Four Noble Truths, one comprehends the characteristics of the truth of suffering through four aspects: the aspect of impermanence, the aspect of suffering, the aspect of emptiness, and the aspect of non-self; comprehends the characteristics of the truth of the origin [of suffering] through four aspects: the aspect of cause, the aspect of accumulation, the aspect of arising, and the aspect of condition; comprehends the characteristics of the truth of cessation [of suffering] through four aspects: the aspect of cessation, the aspect of tranquility, the aspect of sublimity, and the aspect of liberation; and comprehends the characteristics of the truth of the path [to cessation] through four aspects: the aspect of the path, the aspect of fitness, the aspect of accomplishment, and the aspect of deliverance. These methods collectively are called the comprehension of characteristics.

This passage introduces the general practice concerning the Four Noble Truths. The cultivation of each truth comprises four aspects, totaling sixteen aspects together, known as the four truths with sixteen aspects.