Al-Zuhri (may Allah have mercy on him) was asked about the hadd punishment of a slave for wine, and he said that it is half (the punishment) compared to a free man, and that it has reached us that Sayyiduna Umar (may Allah be pleased with him), Uthman (may Allah be pleased with him) and Ibn Umar (may Allah be pleased with them both) used to give a slave half the hadd punishment.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17548