Arabic hadith text
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي الزُّبَيْرِ الْمَكِّيِّ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، أُتِيَ بِنِكَاحٍ لَمْ يَشْهَدْ عَلَيْهِ إِلاَّ رَجُلٌ وَامْرَأَةٌ فَقَالَ هَذَا نِكَاحُ السِّرِّ وَلاَ أُجِيزُهُ وَلَوْ كُنْتُ تَقَدَّمْتُ فِيهِ لَرَجَمْتُ ‏.‏
Translation

Yahya related to me from Malik from Abu'z-Zubayr al-Makki that acase was brought to Umar about a marriage which had only beenwitnessed by one man and one woman . He said, "This is a secretmarriage and I do not permit it. Had I been the first to come upon it,I would have ordered them to be stoned."