Isaiah 6:8 "Also I heard the voice of the Lord, saying: "Whom shall I send, And who will go for Us?" (NKJV)
Here is an occasion when God the Father speaks using the first person plural. We have noticed before, the occasions in Genesis 1:26 and 11:7, when the speaker uses "us" of Himself, He includes His heavenly council along with Him. The voice of God the Father is unmistakeably heard in the Old Testament. (Haggai 2:5,6 ).
Exodus 14:19 "And the Angel of God, who went before the camp of Israel, moved and went behind them;" (NKJV)
This was one of the members of the Godhead protecting Israel from Pharaoh. This angel of God is called Jehovah in Exodus 13:21-22, and 14:21-25,31. This angel of the Lord appears in the Old Testament as the messenger of God, but constantly acts and speaks in a way which implies He is God Himself. All divine titles are given to Him, and worship is offered also. Here are other references to look up. (Genesis 16:10-13; 18:13,14,19,25,32; 22:11; 48:15-16; Exodus 3:2,6,14; 23:20; Joshua 5:13- 15; Judges 6:11; 13:8 ). God the Son is unmistakeably active in the Old Testament Scriptures. His personality and divinity are clearly revealed. (Zechariah 3:1 ). He is of old, even from everlasting (Micah 5:2 ). The mighty God (Isaiah 9:6 ). The Lord of David (Psalm 110:1 ). He was to be born of a virgin (Isaiah 7:14 ). And to bear the sins of many (Isaiah 53:12 ).
Genesis 1:2 "And the Spirit of God was hovering over the face of the waters." (NKJV)
Here, God the Holy Spirit is involved as co-creator of the world. Creative power is a dominant feature of the Holy Spirit's activities. (Job 26:13; Psalm 104:27-30; 147:14-18 ). As "the breath of the Almighty" Genesis 2:7; Job 33:4 ), He is the direct agent in the creation of man. Generation and regeneration are among His activities (Psalm 51:10 ). The Holy Spirit is prominent in the Old Testament as the inspirer of the prophets (Micah 3:8; 2 Peter 1:21 ). The Spirit is witnessed as giving wisdom, strength and goodness to statesmen and warriors and to the people of God (Exodus 31:3; Judges 3;10 ).