Send it not empty. — The advice was to propitiate with gifts the powerful Hebrew Deity, whom they imagined was offended and angry at the insult offered Him — the being placed in an inferior position in the Dagon temple.
The priests and diviners evidently thought that the Hebrew Deity, in some way resident in the “golden chest,” was a childish, capricious deity, like one of their own loved gods — Dagon, or Beelzebub, lord of flies. Their people had insulted Him; He had shown Himself powerful enough, however, to injure His captors, so the insults must cease, and He must be appeased with rich offerings.