Sayyiduna Ibn Umar (may Allah be pleased with them both) said: I was travelling with Sa'd (may Allah be pleased with him). He urinated, then performed ablution and wiped over his leather socks, then led the people in prayer. I objected to him about that. He said: "Will you accept (the opinion of) your father (Umar, may Allah be pleased with him)?" I said: "Yes." So we gathered before the Commander of the Believers, and Sa'd (may Allah be pleased with him) said to him: "I urinated, then performed ablution and wiped over my leather socks, then prayed." Umar (may Allah be pleased with him) said: "You did well and you followed the Sunnah." Sa'd said: "Your son Abdullah objected to me about that." Umar (may Allah be pleased with him) said: "O Sa'd, you were older than him and more knowledgeable."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 85