While we don't know much about Saint Anastasius, we do know that he was born in Rome and succeeded Siricius as Pope. He counted great saints among his friends - Saint Augustine, Saint Jerome and Saint Paulinus were all friends and Saint Jerome wrote that he was a man of great holiness rich in his poverty. He was the first Pope to fight against the writings of Origen, calling a council in 400 AD to formally condemn then. In his letter shortly after to Simplcianus he wrote:
If Origen has put forth any other writings, you are to know that they and their author are alike condemned by me. The Lord have you in safe keeping, my lord and brother deservedly held in honour.
Pope Anastasius also championed Catholics who were pushing back against Donatism (that argued Christian clergy must be utterly faultless for their ministry to be effective) and taught priests how they were to stand and bow their head when reading from the Holy Gospels. After his death on December 19th, 401 AD, he was buried in the Catacomb of Pontian and was succeeded by his son as Pope Innocent I.