Question: "What does it mean that God is truth?"
Answer: Any statement beginning with the words God is indicates that it is ontological in nature; that is, the statement refers to an attribute of God’s being. The attributes of God are typically categorized into two groups, with the first being nonmoral attributes (e.g., eternality, infinity, and omnipotence) and the second being moral attributes, one of which is truth. The statement God is truth speaks to God’s morality.
To say that God is truth is to acknowledge that truth itself proceeds from the nature of God. While many things can have the truth, only one thing can be the truth, with that one thing being God Himself.
Scripture refers to this fact about God directly in a number of places. For example, Jesus said, “I am the way, and the truth, and the life” (John 14:6), and He called the Holy Spirit “the Spirit of truth” (John 14:17; 15:26; 16:13). A more indirect affirmation that God is truth is Hebrews 6:18, which says that “it is impossible for God to lie.”
The Hebrew term for “truth” is emet, which means “truth,” “firm,” “stable,” and “faithful.” The Greek word for “truth” is aletheia, which denotes being “truthful” or “upright” or “having nothing to hide.” From these terms—and from other attributes of God that support His truthfulness such as His immutability (God cannot change), infinity, and simplicity (God cannot be partly anything)—we understand that God Himself is absolute truth. That truth will never change and can always be relied upon.
Lastly, one often overlooked aspect of truth in the Scriptures that applies to God is the synonymous relationships between righteousness and truth, and between unrighteousness and falsehood. For example, Paul refers to people who “do not obey the truth, but obey unrighteousness” (Romans 2:8), and he highlights the equality of unrighteousness and lies and righteousness and truth in Romans 3:5, 7. From this we learn that God’s moral attribute of truth is also tied to His attribute of holiness.