The Khutbatul Wada (Farewell Khutba) is called by that name not because it was the last Khutba of Rasoolullah(S) but because it was his farewell message to all humanity until the end of time. Farewell messages are important because those delivering them wish to state the essence of their principles; the most important aspects of what they stood for and what they want us to remember and practice. This is the message is the essence of Islam and a good introduction to what Islam stands for.