Nafi' (may Allah have mercy on him) says: The iqamah was called in a mosque on the outskirts of Madinah. Ibn Umar (may Allah be pleased with them both) had land near that mosque which he worked. The imam of that mosque was his freed slave, and that freed slave and his companions lived there. When they learned that Ibn Umar (may Allah be pleased with them both) had come for the prayer, they said: "Go forward and lead the congregation." Ibn Umar (may Allah be pleased with them both) said: "You have more right to lead the congregation in your own mosque." So his freed slave led the congregation.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5325