It is narrated from Sayyiduna Ibn Amr (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "If a slave is promised freedom upon paying one hundred uqiyah as the price of his contract of manumission, and he pays ninety uqiyah but then becomes unable (to pay the rest), then he will remain a slave (until he completes the full payment)."