The one, true, creator God “has life in himself (Exod 3:14, John 5:26) and lives eternally (Gen 21:33, Job 36:26, Ps 90:2, Ps 102:12, Isa 40:28, Isa 41:4, Rom 1:20, Rom 16:26, 1 Tim 6:16, Rev 1:8) in glorious light and sovereign love in three persons—Father, Son and Holy Spirit—co-equal in nature, majesty and glory.” When speaking about God, people should describe him as triune—existing as three-in-one. There is God-the Father, God-the Son and God-the Holy Spirit existing as one God. In other words, there is unity as three persons of one substance. There is a divine triune community in loving relationship with one another and working with one another in performing the theo-drama. Athanasius explained the early orthodox Christian view of the Trinity by writing,
…We worship one God in trinity and the trinity in unity, neither blending their persons nor dividing their essence. For the person of the Father is a distinct person, the person of the Son is another, and that of the Holy Spirit still another. But the divinity of the Father, Son, and Holy Spirit is one, their glory equal, their majesty coeternal…Thus the Father is God, the Son is God, the Holy Spirit is God. Yet there are not three gods; there is but one God. The Father was neither made nor created nor begotten from anyone. The Son was neither made nor created; he was begotten from the Father alone. The Holy Spirit was neither made nor created nor begotten; he proceeds from the Father and the Son… Nothing in this trinity is before or after, nothing is greater or smaller; in their entirety the three persons are coeternal and coequal with each other.
Therefore, Christians “believe in one God…the Father almighty… in one Lord Jesus Christ, the only Son of God, begotten from the Father before all ages… in the Holy Spirit, the Lord, the giver of life. He proceeds from the Father and the Son, and with the Father and the Son is worshiped and glorified.”
God is spiritual, meaning that he is immaterial and non-physical in nature. Jesus said, “God is spirit, and his worshipers must worship in the Spirit and in truth” (John 4:24 NIV). Spirit is the life axiom in human beings, and so when worshipers declare that God is spirit, they are acknowledging that God is the life source of everything.
God is a personal being capable of thought, feeling, will, and interaction with other persons. He is not an impersonal force. At the outset in Genesis 3, God personally pursues Adam and Eve and talks to them on a regular basis. This is also seen in the life of Abraham and throughout the history of Israel. God’s people viewed God as a personal God who had a name, and so they called on his name (Gen 4:26, 12:8, Ps 20:9).
God is infinite, and so he has no limits and cannot be limited. Thus, he is omnipresent, specifically meaning that he is everywhere cognizant and active (1 Kgs 8:27, 2 Chr 6:18, Ps 139:7-10, Jer 23:24, Acts 17:24,28), omniscient (Job 37:16, Isa 44:7-8, 25-28, Rom 8:29, 1 John 3:20), omnipotent (Gen 18:14, Job 42:2, Jer 32:27, Matt 19:26, Luke 1:37, 2 Cor 6:18, Rev 1:8). God is immutable, meaning that he does not change either quantitatively or qualitatively. The psalmist declares, God, who is enthroned from of old, who does not change (Ps 55:19 NIV). “According to the prophet Malachi, Israel’s rescue is rooted in God’s unchanging nature: ‘I the LORD do not change, so you the descendants of Jacob are not destroyed (Mal 3:6)’.” James writes that God “does not change like shifting shadows” (Jas 1:17 NIV). God-the Son “is the same yesterday and today and forever” (Heb 13:8 NIV).
 Erickson, Christian, 238.  Stanley J Grenz, Theology for the Community of God (Grand Rapids, MI: W.B. Eerdmans, 2000) EPUB edition, pt. 1, ch. 3, “God is spirit.”  Erickson, Christian, 239-240.  Michael F Bird, Evangelical Theology: A Biblical and Systematic Introduction (Grand Rapids: Zondervan, 2013), EPUB edition, pt. 220.127.116.11 “The God Who is Unlike Us: The Incommunicable Divine Attributes.”  “Triune God” in A Reforming Catholic Confession https://reformingcatholicconfession.com/  Articles of Religion, “Of the Faith in the Holy Trinity.” http://anglicansonline.org/basics/thirty-nine_articles.html  “Athanasian Creed” https://www.crcna.org/welcome/beliefs/creeds/athanasian-creed  “Nicene Creed” https://www.crcna.org/welcome/beliefs/creeds/nicene-creed