Mark 13:11

“And when they lead you and deliver you up, do not be anxious beforehand what you will say, but whatever is given to you in that hour, that speak, for it is not you who speak but the Holy Spirit.”

Although they would be brought before powerful men they need not be anxious as to what they would say. For God would provide them with words. The Holy Spirit would be in them. Thus they must concentrate on their essential message even while detained, and trust God through His Holy Spirit to provide them with their defence when it was needed. Compare again Matthew 10:19 and Luke 12:11. This is ever true for His people. At the hour of their great need He will direct their words. Here we have a similar promise of the Holy Spirit as a Helper to that in John 14-16.

‘Whatever is given you.' That is, ‘whatever God gives you' but avoiding mentioning the divine name.