While the Father and the Holy Spirit are the ultimate Double Witness of Christ, they are certainly not His only witness.
The Scriptures are a witness (John 5:39). Ellen White’s writings, called by inspiration the Spirit of Prophecy, are also a witness. Read Revelation 19:10 and note that “testimony” can mean “witness.” The Scriptures and the Spirit of Prophecy are two bodies of writings bearing a united testimony/witness of truth.
A single book can be a witness (Deuteronomy 31:26). The Bible is actually two testaments, two witnesses unified as one. It is a book of double witness.
The two witnesses of Jesus can be even further simplified. Fashioned as two “tables of stone,”
“tables of testimony,” “tables of covenant,” the Ten Commandments present the very character of Jesus.
Can the book of double witness be further simplified? Yes. In the fundamental definition of the gospel – 1) God, 2) believe, and 3) the gospel – we find exactly two witnesses in which to believe: “God” and “the gospel.” In the tab, “Turning the Key,” (gospelpattern.org) a study is presented showing that the terms “God” and “the gospel” are, in one sense, synonymous. These terms both denote the name of the Lord, the name of Jesus. On the other hand, we recognize that “God” may refer to the Father, and “the gospel” is the “power of God” (Romans 1:16) which may be understood as the “power of the Spirit” (Micah 3:8, Luke 4:14, Romans 1:4; 15:19, 1 Corinthians 2:4, 2 Timothy 1:7).
The double witness is most simply expressed as “God, the gospel.” It may be said that this is the littlest book of double witness. But then this “book” simply identifies the ultimate Double Witness – the Father and the Holy Spirit, the Feet like two “pillars of fire.”
Any true book of double witness, whether it be the Scriptures + Spirit of Prophecy, the Bible, the Tables of the Covenant, or the Gospel, is written, upheld, and presented only by the Inspiration of God (2 Timothy 3:16), the Hand of the Lord (Deuteronomy 33:2), the Spirit of the Lord (Luke 4:18).