We do not know exactly how Captain John Smith communicated this message to the people of Jamestown. We do not have the written laws from that colony or records of the speeches that were given. What we do have is Smith’s journal in which he said that he spoke those words in arguing with the men of the colony.
In his journals, Smith says that the men of the colonies wanted to sell their tools and even their weapons to the Indians in exchange for food. He says they wanted to give up and leave the colony. In September of 1608, Smith had been elected president of the colony and head of its council. Therefore, it was largely up to him to decide what to do. He says that spoke to them, telling them how things were going to be. In the course of talking to them, he says, he told them that the person who did not work would not eat.
We do not have any independent record of how (or if) Smith said this. Smith says that he gave the order while speaking to the men of the colony. You could call it a speech, or you could call it a discussion/argument. At any rate, Smith says that he presented the order verbally and his journals are the only actual record we have of the order.