Booker T. Washington describes meeting an ex-slave from Virginia in his book Up From Salvery:
I found that this man had made a contract with his master, two or three years previous to the Emancipation Proclamation, to the effect that the slave was to be permitted to buy himself, by paying so much per year for his body; and while he was paying for himself, he was to be permitted to labour where and for whom he pleased.
Finding that he could secure better wages in Ohio, he went there. When freedom came, he was still in debt to his master some three hundred dollars. Notwithstanding that the Emancipation Proclamation freed him from any obligation to his master, this black man walked the greater portion of the distance back to where his old master lived in Virginia, and placed the last dollar, with interest, in his hands.
In talking to me about this, the man told me that he knew that he did not have to pay his debt, but that he had given his word to his master, and his word he had never broken. He felt that he could not enjoy his freedom till he had fulfilled his promise.