俱舍論記 9.77

9.77

「由業所起至劇苦難任」者，由風力故轉胎中箭，足上頭下令趣產門，如經糞團過量閟澁。從此胎中向下轉隨，由逼迫故劇苦難任。或可從此產門出後，轉墮草等，劇苦難任。

"Due to the arising of karma […] severe pain, difficult to endure": due to the power of wind, the arrow in the womb is turned around, feet upward and head downward, causing it to head toward the birth canal, like passing an excessively large, obstructed lump of excrement. Turning and descending from within this womb, due to being compressed, there is severe pain, difficult to endure. Alternatively, after emerging from this birth canal, it falls onto straw or the like, suffering severe pain difficult to endure.