Ps 19:7–9ESV
7 The law of the LORD is perfect,
reviving the soul;
the testimony of the LORD is sure,
making wise the simple;
8 the precepts of the LORD are right,
rejoicing the heart;
the commandment of the LORD is pure,
enlightening the eyes;
9 the fear of the LORD is clean,
enduring forever;
the rules of the LORD are true,
and righteous altogether.

So we have developed the sufficiency of Scripture as Paul has detailed to Timothy. David will help us fill in the blanks as to why the Scriptures are sufficient and their desired effect. This is revealed with a snapshot of David’s view within the context of Psalm 19 “The Law of the LORD is Perfect”. The Psalm appears to have 3 divisions: 2 developed points and 1 conclusion. The first section (vv. 1–6) declares that God’s handiwork (His creation) is read by everyone. The second section (vv. 7–9) states the authority of God’s Word in His Law. And the last section (vv. 10–14) states an observation followed with a request to the Lord in light of all of this. Since we know Scripture interprets Scripture let’s put our summary to the test.

Verses 1-6, the glory of God appears to be the driving force for the entire chapter. This correlates with Ps 24:7–10; 50:6 and Ro 1:19-20. Day and night God pours out His speech and knowledge to all, through all the earth and to the ends of the world. Verse 4 is quoted in Romans 10:18 declaring everyone has an opportunity to hear this voice. In that context He is speaking to the Jews who God will restore and Paul asks the question “But I ask, have they not heard? Indeed they have”. Previously Paul made the case that in Romans 1:20 “For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world in the things that have been made. So they are without excuse.” So not only are the Jews culpable in Romans 10 but according to Romans 1 everybody is without excuse because God’s creation screams there is a God.

Verses 7-9, this is where our memory verse states the sufficiency of the Word as revealed throughout Scripture. We’ll come back to this.

Verses 10-14, the observation states that God’s law is to be desired more than your most valued treasure (that would be gold and honey to them). Why are they to be valued so greatly: Because they warn your servant. This begs the question who is your servant…the one who keeps the warnings (see Matt 19:17; John 8:51, 55; 14:15, 23; 1Tim 6:13; 1Jn 2:4,5; 3:22,24; 5:3) The Psalmist’s request is that God would keep His servant from presumptuous sins; that they would have no dominion over him, then he would be blameless. His request is concluded with another request that may the words of his mouth and the meditations of his heart be acceptable to his Rock and Redeemer. Now that’s a request. May that be said of all who read this.

So to develop verses 7-9. There are six synonyms for God’s Word.
• Law of the Lord-perfect, revives the soul
• Testimony of the Lord-sure, makes the wise simple
• Precepts of the Lord-right, rejoices the heart
• Commandments of the Lord-pure, enlightens the eyes
• Fear of the Lord-clean, endures forever
• Rules of the Lord-true and righteous altogether

So I wonder why all the epithet (you’ll have to look it up)? I will list each word in the Hebrew and see if that helps.
• Law- tôrâh, to-raw´; from 3384; a precept or statute, espec. the Decalogue or Pentateuch:—law.
• Testimony- עֵדוּת ʿêdûwth, ay-dooth´; fem. of 5707; testimony:—testimony, witness
• Precepts- [פִּקּוּד]24 n.m. ψ 19:9 precept (of י׳; proposes thing appointed, charge, cf. √B 2
• Commands- 4687. מִצְוָה mitsvâh, mits-vaw´; from 6680; a command, whether human or divine (collect. the Law):—(which was) commanded (-ment), law, ordinance, precept.
• Fear- 3374. יִרְאָה yirʾâh, yir-aw´; fem. of 3373; fear (also used as infln.); mor. reverence:—× dreadful, × exceedingly, fear (-fulness).
• Rules- 4941. מִשְׁפָּט mishpâṭ, mish-pawt´; from 8199; prop. a verdict (favorable or unfavorable) a just decree.

Knowing very well that there is a broad range for the uses of a word when translated between languages we can rest assured, our Author had a specific intent to His audience. The law of the Lord as revealed in the entirety of His Old and New Testament as approved by Jesus is perfect, it never comes back void and has its desired effect.
The testimony is sure because Jesus stated in John 8:14 14 Jesus answered, “Even if I do bear witness about myself, my testimony is true, for I know where I came from and where I am going”. The surety of His witness to His sheep is clear in John 10:25-26 25 Jesus answered them, “I told you, and you do not believe. The works that I do in my Father’s name bear witness about me, 26 but you do not believe because you are not among my sheep.” Who does this testimony make wise? Jesus stated clearly His works bear witness as to who He is to His sheep.
The precepts, the commands, the fear and the rules of the Lord have their desired effect to His sheep. Why? Jesus closed John 10:26 about Him bearing witness with the entirety of His defense, “27 My sheep hear my voice, and I know them, and they follow me. 28 I give them eternal life, and they will never perish, and no one will snatch them out of my hand. 29 My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father’s hand. 30 I and the Father are one.”” The confidence the sheep have in Him knowing them and them following Him has already been described earlier in the chapter when Jesus explained that Gentiles would be included, they too would hear His voice and they listen. “16 And I have other sheep that are not of this fold. I must bring them also, and they will listen to my voice. So there will be one flock, one shepherd. 17 For this reason the Father loves me, because I lay down my life that I may take it up again. 18 No one takes it from me, but I lay it down of my own accord. I have authority to lay it down, and I have authority to take it up again. This charge I have received from my Father.” (Jn 10:16–18)
The law, testimony, precepts, commandments, and decrees of the Lord are only valuable to those who listen and follow Jesus. The fear of the Lord is truly the beginning of knowledge as Solomon stated (Pro 1:7). So is God’s Word all this to you? Do you listen through it? Do you follow? Your perspective on God’s Word will be your perspective on God…because it’s His Word.