حَدَّثَنِي أَبُو الطَّاهِرِ، وَحَرْمَلَةُ بْنُ يَحْيَى، قَالاَ حَدَّثَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، أَنَّهُ سَمِعَ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ، يَقُولُ قَالَ عُمَرُ بْنُ الْخَطَّابِ وَهُوَ جَالِسٌ عَلَى مِنْبَرِ رَسُولِ اللَّهِ صلى الله عليه وسلم إِنَّ اللَّهَ قَدْ بَعَثَ مُحَمَّدًا صلى الله عليه وسلم بِالْحَقِّ وَأَنْزَلَ عَلَيْهِ الْكِتَابَ فَكَانَ مِمَّا أُنْزِلَ عَلَيْهِ آيَةُ الرَّجْمِ قَرَأْنَاهَا وَوَعَيْنَاهَا وَعَقَلْنَاهَا فَرَجَمَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَرَجَمْنَا بَعْدَهُ فَأَخْشَى إِنْ طَالَ بِالنَّاسِ زَمَانٌ أَنْ يَقُولَ قَائِلٌ مَا نَجِدُ الرَّجْمَ فِي كِتَابِ اللَّهِ فَيَضِلُّوا بِتَرْكِ فَرِيضَةٍ أَنْزَلَهَا اللَّهُ وَإِنَّ الرَّجْمَ فِي كِتَابِ اللَّهِ حَقٌّ عَلَى مَنْ زَنَى إِذَا أَحْصَنَ مِنَ الرِّجَالِ وَالنِّسَاءِ إِذَا قَامَتِ الْبَيِّنَةُ أَوْ كَانَ الْحَبَلُ أَوْ الاِعْتِرَافُ ‏.‏

'Abdullah b. 'Abbas reported that 'Umar b. Khattab sat on the pulpit of Allah's Messenger (PBUH) and said: Verily Allah sent Muhammad (PBUH) with truth and He sent down the Book upon him, and the verse of stoning was included in what was sent down to him. We recited it, retained it in our memory and understood it. Allah's Messenger (PBUH) awarded the punishment of stoning to death (to the married adulterer and adulteress) and, after him, we also awarded the punishment of stoning, I am afraid that with the lapse of time, the people (may forget it) and may say: We do not find the punishment of stoning in the Book of Allah, and thus go astray by abandoning this duty prescribed by Allah. Stoning is a duty laid down in Allah's Book for married men and women who commit adultery when proof is established, or it there is pregnancy, or a confession. Translation Not Available

Book Ref: Sahih Muslim Book 29 Hadith 4194
Web Ref:  Sahih Muslim Book 17 Hadith 1691 a