仁王經疏 3.537

3.537

釋曰：第二、舉喻。喻有三種：初之二喻，喻其現報。如有聲形，響影必逐；有現業處，報定同時故。後之一喻，喻生後報。如人夜書，火滅字在。現業雖滅，二報仍在。或可前二通喻三時，若有三業必有果隨，如聲形處必有響影。

The Commentary says: Second, raising the similes. There are three similes: the first two similes illustrate visible-life retribution. For example, when there is a sound or form, the echo and shadow must follow; wherever there is present karma, the retribution is definitely simultaneous. The latter one simile illustrates rebirth and subsequent retribution. For example, when a person writes at night, the fire is extinguished, but the characters remain. Although the present karma has perished, the two retributions still remain. Or, it may be that the first two generally illustrate the three periods: if there are three types of karma, there must be results that follow, just as where there is a sound or form, there must be an echo or shadow.