One should never answer a call of nature on a piece of water. One should first wash his mouth, thrice with water before eating any food.
उभे मूत्रपुरीषे तु नाप्से कुर्यात् कदाचन॥ अन्नं बुभुक्षमाणस्तु त्रिर्मुखेन स्पृशेदपः।