俱舍論疏 1.132

1.132

論「亦名三有至三有漏故」，釋三有也。三有，三界也。此有漏蘊，與有為因故、與有為依故，三有攝故，亦名有。

The treatise says: "They are also called the three existences... because they are contaminated by the three existences," which explains the "three existences." The three existences are the three realms. Because these contaminated aggregates are causes for the conditioned, provide support for the conditioned, and are subsumed under the three existences, they are also called "existences" (bhava).