Saint Gregory, of Nyssa

Saint Gregory of Nyssa (c. 335–c. 394), also known as Gregory Nyssen, was an early Christian theologian and bishop of Nyssa who served as a key leader of the orthodox party in 4th-century controversies over the doctrine of the Trinity. As one of the three Cappadocian Fathers alongside his brother Basil the Great and Gregory of Nazianzus, he made significant contributions to the Nicene Creed and is notable for being the first recorded person to write against all forms of slavery, declaring it inherently sinful[1][2].