瑜伽論記 12.269

12.269

言唯一住故者，唯一寂處也。依一友故者，依友為師造此業也。或同一住處，共相攝受，同一師學。如水乳，為斯義故身諸毛孔各一毛生也。

Regarding 'because of dwelling in a single place alone': dwelling in a single solitary place. Regarding 'because of relying on a single friend': relying on a friend as a master to perform this karma. Alternatively, they share the same dwelling place, assist each other, and study under the same master, mixing like water and milk; for this reason, a single hair grows from each pore of the body.