The false doctrine of Modalism is the belief that God appears in 3 different Modes or manifestations over time.
1) God the FATHER in the Old Testament
2) God the SON in the Gospels
3) God the SPIRIT since Pentacost
But God has always been the Father, Son and Spirit: Behold my servant, whom I uphold; mine elect, in whom my soul delighteth; I have put my spirit upon him: he shall bring forth judgment to the Gentiles. Isaiah 42:1