Paul commends people for “searching the scriptures daily to see if it is so” checking to see if what he, Paul, teaches is so is not suggesting to go to scripture for proof of what is being taught? What other sources did Paul suggest to use?
You wrote:
“What other sources did Paul suggest to use?”
St. Paul himself learned from Christ and the Church. He already knew the scriptures - the Old Testament - and yet had been a Christ denier. Have you ever read 1 Corinthians 11:23? Apparently not. And you clearly have no clue about 2 Thessalonians 2:15 and 2 Thessalonians 3:6.
John 5:36-39 36But the testimony that I have is greater than that of John. For the works that the Father has given me to accomplish, the very works that I am doing, bear witness about me that the Father has sent me. 37And the Father who sent me has himself borne witness about me. His voice you have never heard, his form you have never seen, 38and you do not have his word abiding in you, for you do not believe the one whom he has sent. 39 You search the Scriptures because you think that in them you have eternal life; and it is they that bear witness about me, 40yet you refuse to come to me that you may have life.
John 5:45-47 45Do not think that I will accuse you to the Father. There is one who accuses you: Moses, on whom you have set your hope. 46For if you believed Moses, you would believe me; for he wrote of me. 47But if you do not believe his writings, how will you believe my words?"
Romans 3:21-26 21But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it— 22the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: 23for all have sinned and fall short of the glory of God, 24 and are justified by his grace as a gift, through the redemption that is in Christ Jesus, 25whom God put forward as a propitiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins. 26It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus.