If a slave marries without his master’s permission, he is a fornicator
Good hadithعن جابر بن عبد الله رضي الله عنهما عن النبي صلى الله عليه وسلم قال: «أَيُّما عَبْدٍ تَزَوَّج بغَيْر إذْن مَوَالِيهِ، فهو عاهِرٌ».
Jābir ibn ‘Abdullāh (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "If a slave marries without his master’s permission, he is a fornicator."
Explanation
The Hadīth means that if a slave marries without the permission of his master, his marriage is invalid and the contract is consequently null and void. The slave would therefore be considered as a fornicator. So, the marriage must be nullified and the slave must be separated from the woman he married without his master’s permission, because slaves are not entitled to get married without their masters’ approval.
Source · Narrated by Ibn Majah - Narrated by At-Termedhy - Narrated by Abu Daoud - Narrated by Ahmad - Ad-Daarimi
From the Hadith Encyclopedia (hadeethenc.com).