“Settle it therefore in your hearts, not to prepare in detail beforehand on how to answer, for I will give you a mouth and wisdom, which all your adversaries will not be able to withstand or to gainsay.”
When such things occur they will not need to prepare clever defences beforehand. (It was usual to prepare long and verbose speeches along with suitable gestures in order to impress the court). For they are assured that Jesus will Himself at that time give them a mouth and wisdom which none will be able to prove wrong or rebut. We note again here Luke's deliberate omission of reference to the Holy Spirit in accordance with his pattern in this last part of the Gospel (but for such an idea compare Mark 13:11; and see Luke 12:12; Matthew 10:20). Instead note how Jesus Himself will be with them in His risen power, as in Matthew 28:20.
‘I will give you a mouth and wisdom.' Compare here God's promise to Moses, ‘I will be with your mouth and teach you what you shall say' (Exodus 4:12). Then He promised that Aaron would be his mouth (Exodus 4:16). The whole of Exodus 4:10-16 is worthy of study in this connection, the difference being that the persecuted Christian will have Christ standing with him rather than just Aaron. Compare Acts 6:10 where the hearing ‘could not withstand the Spirit and wisdom with which he (Stephen) spoke'.