John 18:39

Ye have a custom. The word sunhqeia, custom, originally means intimacy, habitual intercourse, and thence naturally passes into the meaning of habit or custom. Only John puts the statement of this custom into the mouth of Pilate. Matthew and Mark relate it as a fact.

At the Passover [ε ν τ ω π α σ χ α]. More specific than Matthew and Mark, where the expression is general, kata eJorthn, at feast - time.