Abu al-Zinad (may Allah have mercy on him) narrates from the jurists of the people of Madinah that when a slave or a slave-woman commits zina, each of them is to receive fifty lashes, and there is no banishment for them. And they used to say: Whoever incurs a hadd while a slave, and it is not carried out on him until he is freed, his hadd is that of a slave.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 17097