Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Ka'b that in Paradise there is a ruby which has neither a hole nor a joint. In Paradise, there are seventy thousand houses, and in each house, there are seventy thousand houris. Only a prophet, a truthful one, a martyr, a just king, or a person who judges over his own self will enter it. The narrator says, "We asked, O Ka'b, who is the one who judges over his own self?" He replied, "He is the person whom the enemy captures, then gives him the choice to either choose disbelief or to hold firmly to Islam, so he is martyred, and he chooses to remain steadfast on Islam."