Luke 22:6

And he promised, and sought opportunity to betray him unto them in the absence of the multitude.

Cross-references

In Matthew 26:5, the chief priests wanted to avoid a crowd — the same concern Judas exploits by seeking opportunity without one.

Mark 14:2 Parallel

In Mark 14:2, they said 'Not during the festival' — parallel to Judas's plan to betray him away from the crowd.

In Matthew 26:16, from that moment Judas sought opportunity — identical to Luke's account of his seeking.

Mark 14:11 Parallel

In Mark 14:11, Judas sought an opportunity to betray him — the same conspiratorial planning described here.