The character of Barabbas is introduced only in Christian sources--the Gospel of Mark (15:6-15), the Gospel of Matthew (27:15-26), the Gospel of Luke (23:13-25), and the Gospel of John (18:38b-40).
The Gospel of Mark speaks of "a man, called Barabbas, who was in prison with the rebels who had committed murder during the insurrection" (Mk 15:7). Similarly, the Gospel of Luke reports that "this was a man who had been put in prison for an insurrection that had taken place in the city, and for murder" (Lk 23:19.25). The Gospels of Matthew and John do not provide any of these details but refer to Barabbas simply as "a notorious prisoner, called Jesus Barabbas" (Mt 27:16), or "a bandit" (Jn 18:40).
According to Mark and Matthew, releasing a prisoner at the Passover was Pilate's custom ("at the festival [Pilate] used to release a prisoner for them, anyone for whom they asked... So the crowd came and began to ask Pilate to do for them according to his custom", Mk 15:6.8; cf. Mt 27:15). For John instead it was a Jewish custom ("[Pilate] said... You have a custom that I released someone for you at the Passover", Jn 18:23). The detail is missing in the Gospel of Luke, if not in a later glossa at Lk 23:17, which generically affirms that "[Pilate] was obliged to released someone for them at the festival".
All four gospels suggest that it was Pilate's intention to free Jesus, but then he was somehow forced against his will to release Barabbas.
The Gospel of Mark argues that "the high priests stirred up the crowd to have him release Barabbas for them instead... They shouted back... [until] Pilate, wishing to satisfy the crowd, released Barabbas" (Mk 15:11-15).
Similarly, Matthew says that "the chief priests and the elders persuaded the crowds to ask for Barabbas and to have Jesus killed" (27:20), while the wife of Pilate interceded for Jesus against Barabbas (Mt 27:19); at the end "when Pilate saw that he could do nothing but rather that a riot was beginning... he washed his hands... and released Barabbas" (Mt 27:24-26).
The interaction between the crowd and the Jewish authorities gets lost in the later gospels. In Luke Pilate addresses a crowd made of "the chief priests, the leaders and the people... They kept urgently demanding with loud shouts that he should be crucified, and their voices prevailed. So Pilate gave his verdict, that their demand should be granted" (Lk 23:13.23). In the Gospel of John, Pilate summoned "the Jews... but they shouted in reply: Not this man, but Barabbas!" (Jn 18:38.40).
As neither the figure of Barabbas nor the occurrence of an insurrection nor the custom of releasing prisoners at the Passover in Jerusalem are recorded in any sources other than the Gospels, the historicity of these events and the very existence of the character of Barabbas are disputed.
An intriguing question is raised by the name of Barabbas, Jesus bar-Abba (= Jesus son of the Father), which is strikingly identical to that of Jesus of Nazareth. This identity seems to suggest that Barabbas could be a literary "double" of Jesus created either as a rhetorical devise to emphasize by opposition what Jesus was not, or to exonerate Jesus from the political uprising he caused in Jerusalem with his messianic claim and action against the temple.
Gabriele Boccaccini, University of Michigan (June 2010)
Barabbas, in the arts
A quite marginal character in Christian tradition and iconography, Barabbas has taken new life in modern fiction, after the works of Marie Corelli, Michel de Ghelderode and Pär Lagerkvist turned him into a complex and tormented figure. The growing interest in the relation between Jesus and the insurgent movements of his time has also made Barabbas a much more conspicuous presence in contemporary Jesus fictional narratives, where he often plays the role of the recognized leader of the Zealots and is sometimes associate with Judas Iscariot.--Gabriele Boccaccini, University of Michigan (June 2010)
References to Barabbas are limited exclusively to ancient Christian sources (Gospels of Mark, Matthew, Luke, and John).
Mark 15:6-15 (NRSV) -- 6 Now at the festival he used to release a prisoner for them, anyone for whom they asked. 7 Now a man called Barabbas was in prison with the rebels who had committed murder during the insurrection. 8 So the crowd came and began to ask Pilate to do for them according to his custom. 9 Then he answered them, "Do you want me to release for you the King of the Jews?" 10 For he realized that it was out of jealousy that the chief priests had handed him over. 11 But the chief priests stirred up the crowd to have him release Barabbas for them instead. 12 Pilate spoke to them again, "Then what do you wish me to do with the man you call the King of the Jews?" 13 They shouted back, "Crucify him!" 14 Pilate asked them, "Why, what evil has he done?" But they shouted all the more, "Crucify him!" 15 So Pilate, wishing to satisfy the crowd, released Barabbas for them; and after flogging Jesus, he handed him over to be crucified.
Matthew 27:15-26 (NRSV) -- 15 Now at the festival the governor was accustomed to release a prisoner for the crowd, anyone whom they wanted. 16 At that time they had a notorious prisoner, called Jesus Barabbas. 17 So after they had gathered, Pilate said to them, "Whom do you want me to release for you, Jesus Barabbas or Jesus who is called the Messiah?" 18 For he realized that it was out of jealousy that they had handed him over. 19 While he was sitting on the judgment seat, his wife sent word to him, "Have nothing to do with that innocent man, for today I have suffered a great deal because of a dream about him." 20 Now the chief priests and the elders persuaded the crowds to ask for Barabbas and to have Jesus killed. 21 The governor again said to them, "Which of the two do you want me to release for you?" And they said, "Barabbas." 22 Pilate said to them, "Then what should I do with Jesus who is called the Messiah?" All of them said, "Let him be crucified!" 23 Then he asked, "Why, what evil has he done?" But they shouted all the more, "Let him be crucified!" 24 So when Pilate saw that he could do nothing, but rather that a riot was beginning, he took some water and washed his hands before the crowd, saying, "I am innocent of this man's blood; see to it yourselves." 25 Then the people as a whole answered, "His blood be on us and on our children!" 26 So he released Barabbas for them; and after flogging Jesus, he handed him over to be crucified.
Luke 23:13-25 (NRSV) -- 13 Pilate then called together the chief priests, the leaders, and the people, 14 and said to them, "You brought me this man as one who was perverting the people; and here I have examined him in your presence and have not found this man guilty of any of your charges against him. 15 Neither has Herod, for he sent him back to us. Indeed, he has done nothing to deserve death. 16 I will therefore have him flogged and release him." 17 18 Then they all shouted out together, "Away with this fellow! Release Barabbas for us!" 19 (This was a man who had been put in prison for an insurrection that had taken place in the city, and for murder.) 20 Pilate, wanting to release Jesus, addressed them again; 21 but they kept shouting, "Crucify, crucify him!" 22 A third time he said to them, "Why, what evil has he done? I have found in him no ground for the sentence of death; I will therefore have him flogged and then release him." 23 But they kept urgently demanding with loud shouts that he should be crucified; and their voices prevailed. 24 So Pilate gave his verdict that their demand should be granted. 25 He released the man they asked for, the one who had been put in prison for insurrection and murder, and he handed Jesus over as they wished.
John 18:38b-40 (NRSV) --  ...After he [i.e. Pilate] had said this, he went out to the Jews again and told them, "I find no case against him.  But you have a custom that I release someone for you at the Passover. Do you want me to release for you the King of the Jews?"  They shouted in reply, "Not this man, but Barabbas!" Now Barabbas was a bandit.