Does Paul ever actually quote Jesus anywhere as a primary source? "Does Paul ever actually quote Jesus anywhere as a primary source"  

However, I came to that post because of my puzzlement regarding Hebrews 10:5-9.  I believe Paul is generally considered the author of Hebrews. Verses 8-9 are very recognizably in the style of the Talmud. Verses 5-7 seem to be attributed to incarnated Jesus before his resurrection. Doesn't, then, Hebrews 10:5-7 count as "Paul quoting Jesus", and, in fact, is this perhaps the only place outside the Gospels where incarnate Jesus is quoted saying something not also found in the Gospels? Possible he met Jesus prior to his Passion and Death?
Does Paul ever actually quote Jesus anywhere as a primary source?

The short answer is possibly.

Since Paul was not a personal witness of Jesus' words, how could he quote him directly from his public ministry.

However, St. Paul is possibly seen as quoting Jesus on the Road to Damascus when he was converted but the author of the Acts wrote in the third person: Acts 9:3–9.

Although written in the third person here it is:


  As he neared Damascus on his journey, suddenly a light from heaven flashed around him. He fell to the ground and heard a voice say to him, "Saul, Saul, why do you persecute me?"
  
  "Who are you, Lord?" Saul asked.
  
  "I am Jesus, whom you are persecuting," he replied. "Now get up and go into the city, and you will be told what you must do."
  
  The men traveling with Saul stood there speechless; they heard the sound but did not see anyone. Paul got up from the ground, but when he opened his eyes he could see nothing. So they led him by the hand into Damascus. For three days he was blind, and did not eat or drink anything.


It is very conceivable that the Apostle St. Paul passed on this information first hand to the author of the Acts of the Apostles. Did St. Paul recount this event directly to St. Luke presumed author of the Acts of the Apostles does not mention. It is nevertheless possible.

Yet it does that the Apostle St. Paul did in fact quote Our Lord in 1Corinthians 11: 23-26. But this would have been recounted to him from one of the Apostles or Disciples of Jesus:


  For I received from the Lord what I also handed on to you, that the Lord Jesus, on the night he was handed over, took bread, and, after he had given thanks, broke it and said, “This is my body that is for you. Do this in remembrance of me.” In the same way also the cup, after supper, saying, “This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me.” For as often as you eat this bread and drink the cup, you proclaim the death of the Lord until he comes.


For some people, it does seem that St. Paul does not directly quote Jesus:


  Christians have long assumed that Luke’s Acts of the Apostles and Paul’s letters were written to illustrate and apply the things Jesus taught through His words and deeds. Both Acts and the epistles of Paul are Jesus-centered and consistent with all that Jesus taught. Acts describes the emergence of the apostolic church and Paul explains the principles of the gospel of Jesus Christ in ways that made them easily accessible to the diverse Gentile communities of the Roman Empire. In neither case would it have been practical for Luke or Paul to duplicate the detailed records of Jesus’ teaching and ministry that were cherished and carefully preserved by the church.
  
  This argument that Paul must not have been concerned with Jesus as a real person because he didn’t quote Him is based on the underlying assumption that the Gospels’ description of Jesus isn’t accurate. Assuming that a miracle-working Jesus who claimed to be the Son of God with the authority to forgive sin could not really have existed, it offers an alternative explanation for how the Jesus tradition came into being. It claims that Paul created an entirely new religion about Jesus based on his own religious experience expressed in terms common to the religious and philosophical language of his day, transforming a popular teacher into a godlike mythological figure. It postulates that the whole Christian community eventually began to view Jesus in Paul’s mythologized way so that when the four Gospels were eventually written they didn’t contain accurate historical recollections of Jesus’ real life and deeds, but a collection of stories constructed around Paul’s imaginary Jesus.
  
  Paul’s conversion occurred only two or three years after Christ’s ministry. Recent orality studies (studies of how group memories and traditions are preserved in predominantly oral cultures) have also shown that when a group considers a tradition worthy of preservation, it selects individuals to be the official representatives (tradents) of the tradition. These tradents are the experts entrusted with the responsibility to preserve and transmit the tradition. In the case of the early church, tradents listed by Paul himself in his epistles were apostles and eyewitnesses of Christ’s ministry. They included Peter, John the son of Zebedee, the rest of the Twelve, Jesus’ half brother James, Barnabas, Andronicus and Junia, and Silvanus. All of these eyewitnesses would never have allowed Paul to begin teaching something that changed or distorted the Jesus narrative. - Why Didn’t Paul Quote Jesus?


As for your question about Hebrews 10: 5-9, St. Paul would be quoting what one of the other Apostles passed on to him. Jesus himself is quoting Psalm 
40: 6-8. Remember this was written for the Hebrew brethren.


  5 Therefore, when Christ came into the world, he said:
  
  “Sacrifice and offering you did not desire,
      but a body you prepared for me;
  6 with burnt offerings and sin offerings
      you were not pleased.
  7 Then I said, ‘Here I am—it is written about me in the scroll—
      I have come to do your will, my God.’”[a]
  8 First he said, “Sacrifices and offerings, burnt offerings and sin offerings you did not desire, nor were you pleased with them”—though they were offered in accordance with the law. 9 Then he said, “Here I am, I have come to do your will.” He sets aside the first to establish the second.