This Psalm was written by David, who is testifying, in essence: “Lord, your testimonies—your laws, decrees and words—are irrevocable. They are utterly reliable.” The author of Hebrews echoes this, declaring that God’s Living Word is eternal and unchangeable: “the same yesterday, today, and forever” (Hebrews 13:8).
Think about it: There are laws operating in the universe that govern how things work, without exception. Consider the laws that rule the movements of the sun, moon, stars and earth. These heavenly bodies were all put into place when God spoke a word, and since that time they have been ruled by laws that God also spoke into being.
We’re told throughout the New Testament that this great God is our Father and that he takes pity on his children. Hebrews tells us the Lord is touched with the feelings of our infirmities, and that he hears our every cry and bottles every tear. Yet we’re also told that he is the righteous King who judges by his law. And his Word is his constitution, containing all of his legal decrees, by which he rules justly. Everything in existence is judged by his immutable Word.
Simply put, we can hold the Bible in our hands and know, “This book tells me who God is. It describes his attributes, nature, promises and judgments. It is his rule of law, from his own mouth, by which he rules and reigns. And it is a Word to which he has bound himself.”
Every earthly judge is bound to determine the case before him according to the established law. God rules and judges everything before him according to the eternal law—that is, his own established Word. When the Lord makes a ruling, he speaks by his living Word, a Word to which he has bound himself.