A.T. Robertson Commentary Luke 21:14

"Settle it therefore in your hearts, not to meditate beforehand how to answer:" — Luke 21:14 (ASV)

Not to meditate beforehand (μη προμελεταιν). The classical word for conning a speech beforehand. Mr 13:11 has προμεριμναω, a later word which shows previous anxiety rather than previous preparation.

How to answer (απολογηθηνα). First aorist passive infinitive. It is the preparation for the speech of defence (apology) that Jesus here forbids, not the preparation of a sermon.