"The simplicity [of God] is of great importance, nevertheless, for our understanding of God. It is not only taught in Scripture (where God is called “light,” “life,” and “love”) but also automatically follows from the idea of God and is necessarily implied in other attributes. Simplicity here is the antonym of “compounded.” If God is composed of parts, like a body, or composed of genus (class) and differentiate (attributes of different species belonging to the same genus), substance and accidents, matter and form, potentiality and actuality, essence and existence, then his perfection, oneness, independence, and immutability cannot be maintained." - Herman Bavinck, Reformed Dogmatics, Volume 2, 176.
"Simplicity is one of the fundamental characteristics of God. This means that He is not composed of different parts, and also that His being and attributes are one. It may be said that God's perfections are God Himself as He has revealed Himself to man. They are simply so many manifestations of the divine Being. Hence the Bible says that God is truth, life, light, love, righteousness, and so on." - Louis Berkhof, Summary of Christian Doctrine.