Aishah (may Allah be pleased with her) said that he (peace and blessings be upon him) said: "Jibril kept enjoining me so much regarding the neighbour that I feared he would be made a sharer in inheritance, and he kept enjoining me so much regarding slaves that I feared a term would be fixed for them after which they would become free on their own."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15801