If it's one man I like to quote a lot hear on the blog it would be John R. W. Stott. He is the writer of the renown book The Cross of Christ. It was just last saturday that he died and went to be in Christ's presence. This quote of his came to my mailbox from his collection describing the work of the Trinity in the Christian's assurance of their faith and it's worth a share.
The witness of God the Holy Spirit
confirms the word of God the Father
concerning the work of God the Son.