Sayyiduna Abu Mas'ud (may Allah be pleased with him) says: When the Messenger of Allah (peace and blessings be upon him) commanded us to give charity, some of us would go to the market, carry loads and earn one mudd (of grain); yet today some of them have a hundred thousand. (The narrator said:) I think he meant only himself.
Imam al-Shafi'i (may Allah have mercy on him) took as evidence the narration of Hanzalah bin Qays from Sayyiduna Rafi' bin Khadij (may Allah be pleased with him) about renting out land for gold and silver, and the fact that more than one of the Companions of the Messenger of Allah (peace and blessings be upon him) practised hiring.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المساقاة / 11647