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 ‏.‏

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." Translation Not Available

Book Ref: Muwatta Imam Malik Book 28 Hadith 1120
Web Ref:  Muwatta Imam Malik Book 28 Hadith 26