Musnad Ahmad 249
It was narrated that Yahya said:
I heard Sa`eed bin al-Musayyab (say) that `Umar (رضي الله عنه ) said: Beware of neglecting the verse of stoning, lest someone say, We do not find two hadd punishments in the Book of Allah, for I saw the Prophet (ﷺ) stone [adulterers] and we stoned [adulterers] too.
حَدَّثَنَا يَحْيَى، عَنْ يَحْيَى، قَالَ سَمِعْتُ سَعِيدَ بْنَ الْمُسَيَّبِ، أَنَّ عُمَرَ، رَضِيَ اللَّهُ عَنْهُ قَالَ إِيَّاكُمْ أَنْ تَهْلِكُوا عَنْ آيَةِ الرَّجْمِ لَا نَجِدُ حَدَّيْنِ فِي كِتَابِ اللَّهِ فَقَدْ رَأَيْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَدْ رَجَمَ وَقَدْ رَجَمْنَا‏.‏