It really depends on what body of Luther's output you're referencing - Luther as a rather acerbic German man swore and cussed a lot and used all sort of sources

It really depends on what body of Luther's output you're referencing - Luther as a rather acerbic German man swore and cussed a lot and used all sort of sources for political arguments. Luther in his output that he would have felt as proclaiming the Gospel, primarily used scripture and early church fathers as the norm. In the Christian tradition, scripture is God-breathed and is a primary source (along with tradition that has been handed down.)