維摩經玄疏 1.43

1.43

六、究竟即者，即是妙覺。一念相應，盡不思議實相之境故。《法華經》云「唯佛與佛，乃能究竟諸法實相」。又《仁王經》云「三賢、十聖忍中行，唯佛一人能盡源」，盡源者，是究竟即也。

Sixth, as for ultimate identity: this is marvelous enlightenment, because in a single thought corresponding [with reality], one exhausts the realm of the inconceivable true mark. The Lotus Sūtra states: 'Only a buddha together with a buddha can exhaustively realize the true mark of all dharmas.' Furthermore, the Benevolent King Sūtra states: 'The three [stages of] worthies and ten [stages of] sages practice within forbearance; only the Buddha alone can exhaust the source.' 'Exhausting the source' is ultimate identity.