The divine revelation that the Old Testament records was conveyed in two principal ways—by mighty works and prophetic words. These two modes of revelation are bound up indissolubly together. The acts of mercy and judgment by which the God of Israel made himself known to his covenant people would not have carried their proper message had they not been interpreted to them by the prophets—the “spokesmen” of God who received and communicated his word. For example, the events of the Exodus would not have acquired their abiding significance for the Israelites if Moses had not told them that in these events the God of their fathers was acting for their deliverance, in accordance with his ancient promises, so that they might be his people and he their God. On the other hand, Moses’ words would have been fruitless apart from their vindication in the events of the Exodus.
F.F. Bruce, New Bible Dictionary, page 138