The impenitent thief is a man described in the New Testament account of the Crucifixion of Jesus. In the Gospel narrative, two criminal bandits are crucified alongside Jesus. In the first two Gospels, they both join the crowd in mocking him. In the version of the Gospel of Luke, however, one taunts Jesus about not saving himself and them, and the other asks for mercy.
In apocryphal writings, the impenitent thief is given the name Gestas, which first appears in the Gospel of Nicodemus, while his companion is called Dismas. Christian tradition holds that Gestas was on the cross to the left of Jesus and Dismas was on the cross to the right of Jesus. In Jacobus de Voragine's Golden Legend, the name of the impenitent thief is given as Gesmas. The impenitent thief is sometimes referred to as the "bad thief" in contrast to the good thief.
The apocryphal Arabic Infancy Gospel refers to Gestas and Dismas as Dumachus and Titus, respectively. According to tradition – seen, for instance, in Henry Wadsworth Longfellow's The Golden Legend – Dumachus was one of a band of robbers who attacked Saint Joseph and the Holy Family on their flight into Egypt.