Reference for Yoma 59:1
מצוה לשפשף מסייע ליה לרבי אמי דאמר רבי אמי אסור לאדם שיצא בניצוצות שעל גבי רגליו מפני שנראה ככרות שפכה ומוציא לעז על בניו שהן ממזרים
the right thing to wipe off [squirtings]. This supports the view of R'Ammi who says: A man must not go out with squirtings on his feet, because he may appear as one that has his privy member cut off and he may thus cause evil talk against his children that they are bastards.<span class="x" onmousemove="('comment',' Men afflicted with such blemish are incapable of reproduction, hence people, mistaking him for a man thus afflicted and hearing that he has children, will spread the rumour that they are begotten in adultery.');"><sup>1</sup></span> R'Papa said: If there be excrement in its place,<span class="x" onmousemove="('comment',' In the anus.');"><sup>2</sup></span>