成唯識論演祕 2.180

2.180

釋曰：既差別相而故知有動至餘方也。《俱舍》亦云：動名身表，以身動時由業動故。

The explanation says: precisely because there are distinct characteristics, it is therefore known that there is movement to another location. The Kośa also states: 'Movement is called bodily communicative action, because when the body moves, it moves due to karma.'