金光明經文句記 3.41

3.41

初、修因相。四枯即空、四榮即假、雙非即中，說有次第、修無前後，乃一心三觀也。故佛於其四枯四榮雙樹中間般涅槃者，正表於此。

First, the characteristics of cultivating the cause. The four withered [trees] are emptiness, the four flourishing [trees] are provisionality, and the double negation is the Middle. In explanation there is a sequence, but in cultivation there is no before and after; this is the threefold contemplation in a single mind. Therefore, that the Buddha entered parinirvāṇa between the twin trees of four withered and four flourishing precisely symbolizes this.