Musnad Ahmad 788:53

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Abu al-Tayyah, who said: A tall, dark-skinned man narrated to me—and Abu al-Tayyah began to describe him—that he came to Basra with Ibn ‘Abbas, and he wrote to Abu Musa. Abu Musa wrote back to him that the Messenger of Allah (peace and blessings of Allah be upon him) was walking, and he inclined toward a soft patch of ground beside a wall and urinated. Then he said: "The Children of Israel, when one of them would urinate and some of his urine would touch him, he would follow it and cut it away with scissors." And he said: "If one of you wishes to urinate, let him seek a suitable place for his urine."