Sa'id bin al-Musayyib (may Allah have mercy on him) said: Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said: Beware lest you perish by abandoning the verse of stoning, with someone saying, 'We do not find two prescribed punishments in the Book of Allah, the Mighty and Majestic.' The Messenger of Allah (peace and blessings be upon him) carried out stoning, and we carried out stoning. By the One in whose hand is my soul, were it not that people would say, 'Umar has added to the Book of Allah,' I would have written it: 'Al-shaykhu wal-shaykhatu idha zanaya farjumuhuma al-battata' (When the old man and the old woman commit adultery, stone them both outright), for we certainly recited it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 16920