Marco 13:11

Be not anxious beforehand what ye shall speak

(μη προμεριμνατε τ λαλησητε). Negative with present imperative to make a general prohibition or habit. Jesus is not here referring to preaching, but to defences made before these councils and governors. A typical example is seen in the courage and skill of Peter and John before the Sanhedrin in Acts. The verb μεριμναω is from μεριζω (μερις), to be drawn in opposite directions, to be distracted.

See on Mateo 6:25. They are not to be stricken with fright beforehand, but to face fearlessly those in high places who are seeking to overthrow the preaching of the gospel. There is no excuse here for the lazy preacher who fails to prepare his sermon out of the mistaken reliance upon the Holy Spirit. They will need and will receive the special help of the Holy Spirit (cf. Marco 13:14-16).