The impenitent thief, called Dysmus in the apocryphal Gospel of Nicodemus. In Longfellow's Golden Legend Dumachus and Titus were two of a band of robbers who attacked Joseph in his flight into Egypt. Titus said, “Let these good people go in peace,” but Dumachus replied, “First let them pay for their release.” Upon this Titus gave his fellow-robber forty groats, and the infant Jesus said—
When thirty years shall have gone by, I at Jerusalem shall die . . . On the accursëd tree. Then on my right and my left side, These thieves shall both be crucified; And Titus thenceforth shall abide In Paradise with me.
The Miracle Play, iii.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894