On 22 May 337, ill and fearing that death would soon come upon him, Emperor Constantine I was baptized in Nicomedia – though he promised to live a better life should he recover.

Constantine had wanted to be baptized in the Jordan but instead was baptized by the Arian bishop Eusebius of Nicomedia on his deathbed as was the traditional practice at the time, so as to be cleansed from all the sins he had committed during his life.

Eusebius relates the account of Constantine’s baptism, noting that he was baptized in the “usual manner” and that after baptism Constantine dressed himself in white rather than the usual imperial purple. Eusebius also relates these words from Constantine, “Now I know that I am truly blessed: now I feel assured that I am accounted worthy of immortality, and am made a partaker of Divine light.”

Constantine died later that day.

Eusebius on the Baptism of Constantine