瑜伽論記 7.344

7.344

由彼破壞最初所有正道根本等者，此中意謂戒為正道根本，今破戒故名壞道根。

Regarding "because they destroy the very initial root of the noble path" and so on: the meaning here is that morality is the root of the noble path; now, because they break morality, it is called destroying the root of the path.