Sahih al-Bukhari, Volume 7, Book 71, Hadith 662 (USC-MSA) ⓘ
Narrated `Abdullah bin `Umar: Two men came from the East and addressed the people who wondered at their eloquent speeches On that Allah's Messenger said. Some eloquent speech is as effective as magic.'
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ ـ رضى الله عنهما أَنَّهُ قَدِمَ رَجُلاَنِ مِنَ الْمَشْرِقِ، فَخَطَبَا، فَعَجِبَ النَّاسُ لِبَيَانِهِمَا، فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّ مِنَ الْبَيَانِ لَسِحْرًا ـ أَوْ ـ إِنَّ بَعْضَ الْبَيَانِ لَسِحْرٌ " .
also referenced under: Book 76, Hadith 81 (In-Book) & Hadith 5767 (DarusSalam)