Abd al-Aziz bin Abi Hazim relates: I heard my father say: I saw Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) urinating the way old men do, standing, as if it were about to escape him. Then he performed ablution (wudu) and wiped over his two leather socks. I said: Why do you not take them off? He said: "I saw one who was better than both me and you doing this."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5874