Sabellianism is an extention of the Trinitarian error of Modalism.  It was taught by Sabellius in Rome early in the third century. He taught that the divine “monad” (the true God behind the Father, Son, and Spirit) expanded itself successively in its revelation to man.  Through these modes, God revealed different aspects of itself.  As the Father, it revealed itself as Creator and Lawgiver, as Son it revealed itself as Redeemer, as Spirit it revealed itself as Comforter and giver of Grace¹.  See Modalism for related Scripture.