A.T. Robertson Commentary John 18:39

"But ye have a custom, that I should release unto you one at the passover: will ye therefore that I release unto you the King of the Jews?" — John 18:39 (ASV)

A custom (συνηθεια). Old word for intimacy, intercourse, from συνηθης (συν, ηθος), in N.T. only here, 1 Corinthians 8:7; 11:16. This custom, alluded to in Mr 15:6; Matthew 27:15, is termed necessity (αναγκη) in Lu 23:17 (late MSS., not in older MSS.). All the Gospels use the verb απολυω (release, set free). Then ινα απολυσω is a subject clause (ινα and first aorist active subjunctive) in apposition with συνηθεια.

Will ye therefore that I release? (βουλεσθε ουν απολυσω; ). Without the usual ινα before απολυσω, asyndeton, as in Mr 10:36, to be explained either as parataxis or two questions (Robertson, Grammar, p. 430) or as mere omission of ινα (ibid., p. 994). There is contempt and irony in Pilate's use of the phrase "the king of the Jews."