Fred R. David said this quote

A clear mission statement describes the values and priorities of an organization. Developing a mission statement compels strategists to think about the nature and scope of present operations and to assess the potential attractiveness of future markets and activities. A mission statement broadly charts the future direction of an organization. A mission statement is a constant reminder to its employees of why the organization exists and what the founders envisioned when they put their fame and fortune at risk to breathe life into their dreams.