Sayyiduna al-Zubayr bin al-Awwam (may Allah be pleased with him) said: "Intercede in matters of the hudud as long as the matter has not reached the ruler; but once it reaches the ruler, do not intercede."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17619