The eastern “orthodox,” by virtue of their practice of re-baptizing trinitarian converts to EO, deny the creed: I confess ONE baptism for the remission of sin
“The Old Testament proclaimed the Father openly, and the Son more obscurely. The New manifested the Son, and suggested the Deity of the Spirit. Now the Spirit Himself dwells among us, and supplies us with a clearer demonstration of Himself. For it was not safe, when the Godhead of the Father was not yet acknowledged, plainly to proclaim the Son; nor when that of the Son was not yet received to burden us further (if I may use so bold an expression) with the Holy Ghost; lest perhaps people might, like men loaded with food beyond their strength, and presenting eyes as yet too weak to bear it to the sun’s light, risk the loss even of that which was within the reach of their powers; but that by gradual additions, and, as David says, Goings up, and advances and progress from glory to glory, the Light of the Trinity might shine upon the more illuminated.”
Oratio theol., 5, 26 [= Oratio 31, 26] (PG 36, 161-163).