The Elcesaites, Elkasaites, Elkesaites or Elchasaites were an ancient Jewish Christian sect in Lower Mesopotamia, then the province of Asoristan in the Sasanian Empire that was active between 100 and 400 CE.
[1][2]: 123 [3] The name of the sect derives from the alleged founder, Elkhasaí (Koinē Greek: Ἠλχασαΐ in Hippolytus), Elksai (Ἠλξαί in Epiphanius), or Elkesai (Ελκεσαΐ in Eusebius, and Theodoret).
[5] Alcibiades announced that a new remission of sins had been proclaimed in the third year of Trajan (100 AD), and he described a baptism which should impart this forgiveness even to the grossest sinners.
One who has been bitten by a mad dog is to run to the nearest water and jump in with all his clothes on, using the foregoing formula, and promising the seven witnesses that he will abstain from sin.
[8] Eusebius (History 6.38) records a summary of a sermon on Psalm 82 delivered in Caesarea by Origen c. 240–250 AD which warns his audience against the doctrine of "the Elkesaites".
[9] According to Eusebius, Origen regarded the heresy as quite new, and states that the group deny the writings of Paul, but claim to have received a new book from heaven.
Origen speaks of it in this manner in a public homily on the eighty-second Psalm: "A certain man came just now, puffed up greatly with his own ability, proclaiming that godless and impious opinion which has appeared lately in the churches, styled 'of the Elkesites.'
These are Jews like the former... originally came from Nabataea, Ituraea, Moabitis, and Arielis, the lands beyond the basin of what sacred scripture called the Salt Sea...
[12]The Cologne Mani-Codex (dated from the fourth century) describes the parents of Mani, founder of Manichaeism, as "followers of the prophet Alchasaios", which scholars have identified with Elchasai.
[14] The Codex deals with the Elcesaites extensively, confirms some of the Church Fathers’ statements about them, and depicts Mani as a "reformer" with the purpose to "restore" the true doctrine of prophet Alchasaios, which his followers had "misunderstood".