Musannaf Ibn Abi Shayba 1:1197

Ibn Fudayl narrated to us, from ‘Ata’ ibn al-Sa’ib, who said: Al-Hasan used to dislike that a man should urinate in his place of bathing. They said: And Bakr ibn ‘Abd Allah used to say: "It provokes obsessive whispers (waswasa)."