Tao-sheng: Falling Flowers and Earthquakes

Thereupon the gods rained mandārava-flowers, mahā-mandārava-flowers, mañjūṣaka-flowers, and mahā-mañjūṣaka-flowers upon the Buddha and the great multitude. The world of the Buddha quaked in the six ways.

As [the Buddha] entered and reached the samādhi, his spirit moved heaven and earth. In heaven appear flowers of rain; on earth there is shaking (earthquake). As heaven and earth move, how can men remain silent? Now that good omens have appeared there certainly will be an extraordinary preaching. The general mood at the time is full of speculation, and their doubts deepen. As deep doubts pile up, awakening, [if it happens] would necessarily be deep, too. The four kinds of mandārava flowers poured from heaven are designed to show the unreality of the four kinds of fruition. The trembling of the earth is meant to demonstrate the nonabidingness (or transitoriness) of the four kinds of fruition. Also shown is the fact that the six kinds of living beings are all endowed with [the capacity for] great enlightenment. It shows also [the truth of] impermanence (anitya).

Tao-sheng Commentary on the Lotus Sutra, p170