In the beginning was the Word
In the Bible, the phrase apparently means that the Word of God predated the acts of creation and everything that followed. A mission statement, as it were. I'm no theologist, so don't hold me to that.
What Zubrin means in the context of his article is that what the space program really needs is a powerful statement of a specific and directed mission, probably from the President, to act as a guide for space developments.
The Kennedy statement on going to the Moon is the archetype of such, but no president since then has really managed to do anything similar, although some have tried.