For it is - the Spirit of your Father, etc. - This was an extraordinary promise, and was literally fulfilled to those first preachers of the Gospel; and to them it was essentially necessary, because the New Testament dispensation was to be fully opened by their extraordinary inspiration. In a certain measure, it may be truly said, that the Holy Spirit animates the true disciples of Christ, and enables them to speak. The Head speaks in his members, by his Spirit; and it is the province of the Spirit of God to speak for God. Neither surprise, defect of talents, nor even ignorance itself, could hurt the cause of God, in the primitive times, when the hearts and minds of those Divine men were influenced by the Holy Spirit.
Your Father - This is added to excite and increase their confidence in God.

For it is not ye that speak,.... Not but that they were to speak the words, and did; but then both the things they spoke, and the very words in which they spoke them, were not of themselves, but were suggested and dictated by the Spirit of God; for as "the preparation of the heart" in them, so "the answer of the tongue" by them, were both "from the Lord": the Spirit, he was the efficient cause, they were only instruments; for not they of themselves spoke; or not so much they,
but the Spirit of your father, which speaketh in you, or "by you": what they should say was not to be dictated by their own spirit or natural understanding, nor by an angel, but by the Spirit of God; called the "Spirit of" their "father", because he proceeds from him, is of the same nature with him, and is the reason of his being given to them: and this character of him might serve to strengthen their faith in the expectation of him, and in the assistance promised, and to be had by him; since he was the spirit of him, who stood in the relation of a father to them, and bore a paternal affection for them.

For it is not ye that speak, but the Spirit of your Father which speaketh in you--How remarkably this has been verified, the whole history of persecution thrillingly proclaims--from the Acts of the Apostles to the latest martyrology.