Jesus gave a mission to the disciples just before he left for heaven, his last words on Earth. The same purpose is passed on to us.
Matthew 28:19-20
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you always, even unto the end of the world. Amen.