God speaks only truth

"From eternity to eternity, God expresses the entire fullness of his infinite mind and hears his own word. It is undoubtedly this truth that underlies the conception of the divine Wisdom in the Old Testament and the divine Word (Logos) in the New Testament. The Word which God addresses to himself from eternity to eternity is the Son, who is always 'with God' and essentially is God (John 1:1). Now it pleased God according to his eternal good pleasure to speak concerning himself outside of himself, to let his word proceed outside of himself (ad extra). It should be emphasized that this is not an act of necessity, but of sovereignty, of sovereign freedom, determined by his sovereign eternal counsel." - Herman Hoeksema in Reformed Dogmatics