Kathir bin al-Salt said: We were writing copies of the Mushaf with Zayd bin Thabit (may Allah be pleased with him). When we reached this verse, Zayd (may Allah be pleased with him) said: I heard the Prophet (peace and blessings be upon him) saying: "'Al-shaykhu wal-shaykhatu idha zanaya farjumuhuma al-battata nakalan min Allahi wa rasulihi' (When the old man and the old woman commit adultery, stone them both outright, as an exemplary punishment from Allah and His Messenger)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 16912