Paul cited the Gospel of Luke as scripture
Paul on occasion speaks of his message as "my gospel" (Rom. 2:16; II Tim. 2:8). The mindset, that Paul could not possibly be alluding to any writing when he used the expressions “my gospel” and “our gospel”, is one that needs to be addressed.
Lee Dahn reminds me that Paul, said in 1 Timothy 5:18, for the scripture says, “You shall not muzzle an ox when it is treading out the grain," and, "The laborer deserves his wages” and that Luke 10:7 states: “And remain in the same house, eating and drinking what they provide, for the laborer deserves his wages; do not go from house to house.” You will note the Greek phrase for “the laborer deserves his wages” is the same but I have having trouble posting the Greek.
According to Michael Pahl, “Paul consistently uses "receive" (paralambanō) and "deliver" (paradidōmi) language in "transfer of information" contexts to refer to humanly mediated teaching or tradition (Rom 6:17; 1 Cor 11:2; Gal 1:9; Phil 4:9; 1 Thess 2:13; 4:1; 2 Thess 3:6). This usage parallels contemporary Pharisaic and later Rabbinic "receive" and "deliver" language in reference to humanly mediated teaching or tradition (see e.g. Gerhardsson, Memory and Manuscript, 288-291).”