Abu Hazim (may Allah have mercy on him) said: I saw Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) urinating while standing - he had grown old, to the point that he could hardly control it - then he called for water, performed ablution (wudu) and wiped over his leather socks. I said: Why do you not take off your leather socks? He said: "I have seen someone better than me doing that."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5801