I have heard a number of skeptics argue that Paul’s lack of quotations of Jesus are a serious problem for our understanding of Jesus. Jesus was a well known historical figure, why doesn’t Paul quote him more?
I have written on this topic myself, including this journal article. William Lane Craig addresses this question in this video. I think he nails the issue by pointing out both that the epistles are occasional (written for a specific purpose) and that the claim that Paul doesn’t quote Jesus is overstated. I encourage you to watch this short video.