‘Abdur-Rahman bin ‘Awf narrated that 'Umar bin al Khattab رضي الله عنه addressed the people and he heard him say: Some people say: what is this stoning? ín the Book of Allah it mentions flogging.But the Messenger of Allah (ﷺ) ﷺ stoned and we stoned after him. Were it not that some people would say that 'Umar added something to the Book of Allah that is not part of it, I would have written it the way it was revealed.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا هُشَيْمٌ، حَدَّثَنَا الزُّهْرِيُّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عُتْبَةَ بْنِ مَسْعُودٍ، أَخْبَرَنِي عَبْدُ اللَّهِ بْنُ عَبَّاسٍ، حَدَّثَنِي عَبْدُ الرَّحْمَنِ بْنُ عَوْفٍ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، رَضِيَ اللَّهُ عَنْهُ خَطَبَ النَّاسَ فَسَمِعَهُ يَقُولُ أَلَا وَإِنَّ أُنَاسًا يَقُولُونَ مَا بَالُ الرَّجْمِ فِي كِتَابِ اللَّهِ الْجَلْدُ وَقَدْ رَجَمَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَرَجَمْنَا بَعْدَهُ وَلَوْلَا أَنْ يَقُولَ قَائِلُونَ أَوْ يَتَكَلَّمَ مُتَكَلِّمُونَ أَنَّ عُمَرَ رَضِيَ اللَّهُ عَنْهُ زَادَ فِي كِتَابِ اللَّهِ مَا لَيْسَ مِنْهُ لَأَثْبَتُّهَا كَمَا نُزِّلَتْ.
sunnah.com