Patanjali does something unusual immediately after listing the five yamas. Having named nonviolence, truthfulness, non-stealing, continence and non-possessiveness at sutra 2.30, he adds at 2.31 that these restraints, when not conditioned by class, place, time or circumstance, constitute the great vow, the mahavrata. The qualification is the point. Most duty in the classical Indian world was indexed to who you were: a soldier's obligations differed from a priest's, a householder's from a renouncer's, and the lawbooks spent enormous care on those differences.
The yamas cut across all of it. Nobody, in any station, at any time, in any emergency, is released from them. The commentators spell out what this rules out with uncomfortable examples: a fisherman may reason that his violence is confined to fish and is his livelihood, but the great vow admits no such carve-out. This universality is what makes the yamas the foundation of the eight-limbed path rather than merely its first step. The postures, breath control and meditative absorptions that follow are technical accomplishments; the yamas are the moral bedrock beneath them, and the tradition is blunt that technique without restraint produces power without safety. A practitioner who has not stopped harming, lying and grasping is, on Patanjali's account, building on sand.