Themes on 'Redemption of the Dead' is not only depicted in historical Christian art but it is also found in ancient Christian writings. 'Baptism for the Dead' is just one aspect of this concept of redeeming the dead that was taught by the Early Christian Church.
Loss of the Belief in Redemption For The Dead
Justin Martyr [A.D. 110-165], wrote a polemical work that responded to some of the early anti-Christian Jews. He accused some of them having removed from some of the copies of the sayings of Jeremiah a prophecy that predicted Christ's descent. "The Lord God remembered His dead people of Israel who lay in the graves; and He descended to preach to them His own salvation."
Lundy gives another translation of this prediction as it was recorded by Irenaeus: "`And the Lord remembered His dead saints (Israel) who slept in the land of sepulture; and He went down to preach His salvation to them, and to rescue and save them.'" (Justin Martyrs, Dialogue with Trypho, LXXII, 4)