It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever frees a slave according to his share, it is incumbent upon him to free him completely, provided he possesses enough wealth that, according to the estimation of a just man, equals the value of the slave. If he does not have wealth, then only the portion he has freed will remain freed."