In the Christian New Testament Joseph Justus (also known as Barsabbas) figures momentarily in the casting of lots among the 120 or so gathered together after the Ascension of Christ, to replace Judas Iscariot and bring the Apostles again to the number twelve. According to Acts of the Apostles i.23 – 26:
23.So they proposed two men: Joseph called Barsabbas (also known as Justus) and Matthias. 24.Then they prayed, "Lord, you know everyone's heart. Show us which of these two you have chosen 25.to take over this apostolic ministry, which Judas left to go where he belongs." 26.Then they cast lots, and the lot fell to Matthias; so he was added to the eleven apostles."
Since the passage identifies the candidates as "of these men which have companied with us all the time that the Lord Jesus went in and out among us, beginning from the baptism of John, unto that same day that he was taken up from us", Joseph was a member of the wider circle of disciples.
Further identification of this shadowy figure is insecure, though in Christian tradition, he is numbered among the Seventy Disciples mentioned in Luke 10:1-24. No names are given among the Seventy-Two or Seventy Apostles of Christ—depending on the manuscripts—that were sent out in Luke 10.1:"two by two, into every town and place where he himself was about to go." Nor is this "Joseph the Just, son of the 'Father'"—as his name translates— identified as one of the adelphoi of Jesus— however this Greek word for "brothers" may be interpreted—in this one passage in Acts in which he appears. Nor does such a "Joseph Justus" appear among the disciples in the lists given in the synoptic gospels, unless he were represented unrecognized in some way under an alias. It would appear to be an inexplicable choice made by Peter among the assembled adelphoi (Acts 1.15, translated in the New International Version "believers").
However, there are both a Joses and a James the Just among the adelphoi of Jesus. Joses is mentioned in the Gospel of Mark 6:3. Where the passage is repeated in Matthew, 13:54 - 57, "Joses" is rendered "Joseph" instead. Robert Eisenman has read this shadowy figure of "Joseph Justus" as a cloned conflation who represents in a single figure all the Desposyni—rejected, according to the author of Acts in favor of an otherwise unknown Matthias (Eisenman 1997) .
In Christian tradition, this Justus went on to become Bishop of Eleutheropolis, where he died a martyr and is venerated as Saint Justus of Eleutheropolis. The location provides a date for this legend, since the site of Eleutheropolis was a mere village in the 1st century, whose inhabitants were slain and enslaved with others by Vespasian in AD 68 (Josephus, Bell. Jud). The site was refounded, as Eleutheropolis, in AD 200 by Septimius Severus. However, and a first historical bishop can be found in the 4th century, when Eleutheropolis was an important city.