The pillow is a silent Sibyl, and to sleep upon an enterprise avails more than to be sleepless under it.

[Es la almohada Sibila muda, y el dormir sobre los puntos vale más que el desvelarse debajo de ellos.]

Baltasar Gracián y Morales (1601-1658) Spanish Jesuit priest, writer, philosopher

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 151 (1647) [tr. Fischer (1937)]
    (Source)

(Source (Spanish)). Alternate translations:

The Pillow is a dumb Sibylle. To sleep upon a thing that is to be done, is better than to be awaked by a thing already done.
[Flesher ed. (1685)]

The pillow is a silent Sibyl, and it is better to sleep on things beforehand than lie awake about them afterwards.
[tr. Jacobs (1892)]

The pillow is a tongueless sibyl, and it is better to sleep on something than to lie awake when things are on top of you.
[tr. Maurer (1992)]