Nafi' (may Allah have mercy on him) said: Sayyiduna Ibn Umar (may Allah be pleased with them both) would not go to the bathhouse to remove his hair but would do it in the room, and he would wear a waist-wrap (izar). He would order me to apply it to the visible parts of his body, so I would apply it; then he would order me to move back, and he would apply it to his private parts himself.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 710