7. The law of the LORD is perfect, restoring 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.
Psalms 19:7-8
Otherwise,it would be redundant to write the New Testament, since the law and testimony and precepts and commandments of the LORD were (as you interpret "perfect") "complete" right then and there when the Psalms were written, in the OT.
However, Scripture --- even, the very excellent Psalm you quoted for me, Psalm 19 itself--- says that God's "report" to us comes through even the natural things He created:
The heavens declare the glory of God;On the basis of this, and many other passages, we know the authority of Natural Law. Its authority is as great as Scriptural Law, and cannot contradict Scriptural Law, because they both have the same Author.
the skies proclaim the work of his hands.
Day after day they pour forth speech;
night after night they reveal knowledge.
They have no speech, they use no words;
no sound is heard from them.
Yet their voice goes out into all the earth,
their words to the ends of the world.
Moreover, even the NT, while perfect,is not "complete" since Jesus said He would send our Lord the Holy Spirit to instruct the Church. And notice the context: this is the Last Supper discourse, where Jesus is talking to His Apostles, the very core of the Apostolic leadership of the Church:
John 14:17Thus the Lord Jesus could say to his 72 disciples,
The world cannot accept him [the Holy Spirit], because it neither sees Him nor knows Him. But you know Him, for He lives with you and will be in you.
John 14:26
But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you.
John 15:26
When the Advocate comes, whom I will send to you from the Father -- the Spirit of truth who goes out from the Father -- He will testify about me.
John 16:13
But when He, the Spirit He will not speak on His own; He will speak only what he hears, and He will tell you what is yet to come.
Luke 10:16-17
"Whoever listens to you listens to Me;
whoever rejects you rejects Me;
and whoever rejects Me rejects the One who sent Me."
The seventy-two returned with joy and said,
"Lord, even the demons submit to us in Your name."
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