The Prophet ﷺ said, "If a slave marries without his master's permission, his marriage is invalid."
حدثنا عقبة بن مكرم حدثنا أبو قتيبة عن عبد الله بن عمر عن نافع
أن النبي ﷺ قال إذا نكح العبد بغير إذن مولاه فنكاحه باطل
No references are available.
[Hasan] Bayhaqi 7/127 narrated it from the hadith of Abu Dawud, with the same chain. Abdullah bin Umar Umari, from Nafi, is a narrator whose hadith is sound, and the preceding hadith supports it.