Matthew 10:19-20 "But when they arrest you, do not worry about what to say or how to say it. At that time you will be given what to say, for it will not be you speaking, but the Spirit of your Father speaking through you."
I fancy that it is every Christian speaker's wish or prayer that the Father will use him/her as a vessel to share God's will with others. Why else would anyone want to do Christian work, if not to be God's disciple?
Here, Jesus was instructing his disciples in how to behave as they ministered to others. He felt it was important for them to know that if they fell victim to arrest for preaching the gospel, God would speak for them. They didn't have to grope for what to say.
How marvelous it would be if everyone who shares God's word with others would ask for the Father's help in saying what is needed. That way, no needs would be left to chance. God's will would be automatically spoken.