acts 9:5 And he said, Who art thou, Lord? And the Lord said, I am Jesus whom thou persecutest: it is hard for thee to kick against the pricks. - Free Bible Online

      5. Who art thou, Lord?--"Jesus knew Saul ere Saul knew Jesus" [BENGEL]. The term "Lord" here is an indefinite term of respect for some unknown but august speaker. That Saul saw as well as heard this glorious Speaker, is expressly said by Ananias (Ac 9:17; 22:14), by Barnabas (Ac 9:27), and by himself (Ac 26:16); and in claiming apostleship, he explicitly states that he had "seen the Lord" (1Co 9:1; 15:8), which can refer only to this scene.
      I am Jesus whom thou persecutest--The "I" and "thou" here are touchingly emphatic in the original; while the term "JESUS" is purposely chosen, to convey to him the thrilling information that the hated name which he sought to hunt down--"the Nazarene," as it is in Ac 22:8 --was now speaking to him from the skies, "crowned with glory and honor" (see Ac 26:9).
      It is hard for thee to kick against the pricks--The metaphor of an ox, only driving the goad deeper by kicking against it, is a classic one, and here forcibly expresses, not only the vanity of all his measures for crushing the Gospel, but the deeper wound which every such effort inflicted upon himself.

JFB.