When Buddha got enlightened on that full moon day in the month of May, he maintained silence for a whole week. All the angels in the heaven got frightened. They knew that it was only once in a millennium that someone blossoms like Buddha. They requested him to say something. He said, "Those who know, know even without my saying it and those who do not know will not know even by my saying it."
Buddha said, "Words cannot convey it. As many scriptures in the past have revealed, truth begins where words end." The angels said, "What you say is right. But consider those who are in between, who are neither fully enlightened nor totally ignorant. For them, a few words will give a push. Please speak for their sake. Every word of yours will create silence." The purpose of words is to create silence. If words create more noise, they have not reached their goal.
[From 'Buddha, Manifestation of Silence' )