首楞嚴義疏注經 1.635

1.635

德長臘高，最初度故，名為長老。佛轉法輪，五人之中陳如先悟。佛問解否，答言已解，因得解名。悟此見修如客如塵，證得無為生空涅槃，湛然不動如主及空，因即獲果。

Because his virtue was senior and his monastic age high, and he was the very first to be delivered, he is called an elder. When the Buddha turned the wheel of Dharma, among the five persons Kauṇḍinya was the first to awaken. When the Buddha asked whether he understood, he replied that he had already understood; thus he obtained the name 'Understanding' (Ājñāta). Awakening to the fact that these seeing and cultivation [defilements] are like guests and dust, he realized unconditioned, emptiness-of-birth nirvāṇa, serenely unmoving like the host and space, and thereupon attained the fruit.