釋禪波羅蜜次第法門 5.13

5.13

第一、釋名者，所言初禪者，禪名支林。行者初得支林之法，故名初禪。復次，覺觀等法，名之為支。行者修初禪覺觀之法，必於前發，故說覺觀名為初禪。

First, regarding the explanation of the name: what is called the "first dhyāna"—"dhyāna" means a grove of factors. A practitioner first attains the dharma of the grove of factors, and therefore it is called the first dhyāna. Furthermore, dharmas such as vitarka and vicāra are called factors. When a practitioner cultivates the first dhyāna, the dharmas of vitarka and vicāra must arise first, and therefore vitarka and vicāra are spoken of as the first dhyāna.