The entrance of thy words giveth light - The Septuagint translates this, “the manifestation (or declaration) - ἡ δήλωσις hē dēlōsis - of thy words enlightens.” So the Vulgate. Luther renders it, “When thy word is revealed, so it delivers us, and makes the simple wise.” DeWette, “The opening (revelation) of thy word,” etc. The Hebrew word - פתח pethach - means an “opening” or “entrance” - as of a gate, Joshua 20:4; Judges 9:35; and then “a door,” as of a tent or the temple, Gen 18:1; 1 Kings 6:8; or the gate of a city, Isaiah 3:26; and then it means opening, insight, instruction. The word as used here seems to denote the opening or unfolding of the word of God; the revelation of that word to the mind. A door is open so that we enter into a house; a gate, so that we enter into a city; and thus the meaning of the word of God is “opened” to us, so that we may, as it were, enter in and see its beauty. The language does not, therefore, denote the entrance of that word into the mind, but, its being made open to us so that we may perceive its beauty, or may ourselves “enter” into its meaning, its mysteries, and its beauties.
It giveth understanding unto the simple - The word rendered “simple” literally means “those who are open to persuasion,” or who are easily enticed or seduced. Then it refers to the credulous, Proverbs 14:15, and then to the “inexperienced.” See Psalms 19:7, note; Psalms 116:6, note.