There is absolutely no problem with the idea that Matthew and/or Luke copied some text from Mark’s Gospel and used it in their Gospels. Perhaps Luke had access to Mark and Matthew and used texts from both of them in his own Gospel. Luke 1:1–4 tells us, “Many have undertaken to draw up an account of the things that have been fulfilled among us, just as they were handed down to us by those who from the first were eyewitnesses and servants of the word. Therefore, since I myself have carefully investigated everything from the beginning, it seemed good also to me to write an orderly account for you, most excellent Theophilus, so that you may know the certainty of the things you have been taught.”
Sinasabi sa atin sa Lukas 1:1-4, "Yamang marami ang nagpilit mag-ayos ng isang kasaysayan noong mga bagay na naganap sa gitna natin, alinsunod sa ipinatalos sa atin nilang buhat sa pasimula ay mga saksing nangakakakita at mga ministro ng salita, ay minagaling ko naman, pagkasiyasat na lubos ng pangyayari ng lahat ng mga bagay mula nang una, na isulat sa iyong sunodsunod, kagalanggalang na Teofilo;Upang mapagkilala mo ang katunayan tungkol sa mga bagay na itinuro sa iyo."