Yogācārabhūmi-śāstra: Volume 34 (17)

How to contemplate the internally produced things being damaged by others and their changing nature of impermanence? It is by observing that either oneself or others are harmed by others, resulting in alterations to their bodies. These may be caused by destruction from knives, sticks, whips, leather straps, ropes, spears, lances, and so forth, or by harmful contacts from various mosquitoes, gadflies, snakes, scorpions, and other venomous creatures. Then at another time, one sees it unchanged. After witnessing these phenomena, one forms this thought: "Such formations are indeed impermanent in nature." The rest is as previously explained.