Serapion was born around the year 400. He was an Egyptian monk. He ran the catechetical school of Alexandria. He resigned from this job to spend more time in prayer and penitence. He was a student of Saint Anthony the Abbot in the desert and was a friend of Saint Athanasius of Alexandria.
He was the Bishop of Thimuis, in the Nile River delta of Egypt in 339. He fought against Arianism. He spoke in support of Athanasius also against Arianism. These views got him banished by Emperor Constantius II for all this opposition to Arianism.
He was named a Confessor of the Faith by Saint Jerome. He also fought again Macedonianism. Macedonianism denies the divinity of the Holy Spirit. He also wrote against Manichaeism, which said only our spirit is good and our body is evil. Serapion said our bodies can be instruments of good or evil. It’s our choice and wicked men can change.
He died around 368 in Egypt while still in exile from the emperor.