38bAnd when he had said this, he went out again to the Jews and said to them, "I find no guilt in Him. 39But you have a custom that I release someone for you at the Passover; do you wish then that I release for the King of the Jews?" 40So they cried out again, saying, "Not this Man, but Barabbas." Now Barabbas was a robber.
Joh_18:39 "you have a custom" This is explained in Mat_27:15 and Luk_23:17 (but unknown from historical documentation outside the NT).
Joh_18:40 "So they cried out again, saying, 'Not this Man, but Barabbas" It is ironical that Barabbas was apparently a member of the zealot party and, therefore, guilty of the very charge for which Jesus was condemned (cf. Mar_15:7; Luk_23:19; Luk_23:25). This crowd apparently had been waiting there to support their local folk-hero. The Jewish authorities just took this opportunity to assure the condemnation of Jesus (cf. Mar_15:11).
It is also ironic that the name "Barabbas" means "son of a father." John uses these plays on words throughout his Gospel. The crowd wanted the "son of the father" released instead of "The Son of the Father." The darkness has fully come!