William Penn was a prolific writer, and, following the practice of the period, he drew upon countless authorities to support his arguments and strengthen the points he wished to make. While he is often remembered for his familiarity with the classics, with church fathers and political philosophers, we should remember that he referred to the Scriptures, and quoted from them more frequently than all other sources combined.
Bronner, Edwin B., "William Penn and the Scriptures" (1996). Truth's Bright Embrace: Essays and Poems in Honor of Arthur O. Roberts. 16.