Preaching On The Holy Spirit

I'm going to do a mini-series on "God, The Holy Spirit" over the next 3 sundays... Keeping in Step with The Spirit by JI Packer is a tremendous resource

(page 59)
"The truth of the Trinity is a New Testament revelation... But should anyone think that according to Scripture God was unipersonal during the Old Testament period and only became tripersonal when Jesus was born, he would be wrong. What is in question here is not the mode of God's being from eternity, but the manner of its revelation in history. I am not saying that the third person of the Godhead did not exist or was not active in Old Testament times; the New Testament writers assure us that He did and was. I am only saying that His distinct personhood is not expressed by the Old Testament writers; though God's triunity is an eternal fact, only through Christ was it made known." --JI Packer