كتاب الزهد والرقائق
55
The Book of Zuhd and Softening of Hearts
(14)
Chapter: The Prohibition Of Praising if It Involves Exaggeration And There Is The Fear That It May Be A Source Of Temptation (Fitnah) For The One Who Is Praised
(14)
باب النَّهْىِ عَنِ الْمَدْحِ، إِذَا كَانَ فِيهِ إِفْرَاطٌ وَخِيفَ مِنْهُ فِتْنَةٌ عَلَى الْمَمْدُوحِ
Sahih Muslim 3000 a

'Abd al-Rahman b. Abu Bakra reported on the authority of his father that a person praised another person in the presence of Allah's Apostle (ﷺ), whereupon he said:

Woe be to thee, you have broken the neck of your friend, you have broken the neck of your friend-he said this twice. If one of you has to praise his friend at all, he should say: I think (him to be) so and Allah knows it well and I do not know the secret of the heart and Allah knows the destined end, and I cannot testify his purity against Allah but (he appears) to be so and so.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، عَنْ خَالِدٍ الْحَذَّاءِ، عَنْ عَبْدِ الرَّحْمَنِ، بْنِ أَبِي بَكْرَةَ عَنْ أَبِيهِ، قَالَ مَدَحَ رَجُلٌ رَجُلاً عِنْدَ النَّبِيِّ صلى الله عليه وسلم - قَالَ - فَقَالَ ‏"‏ وَيْحَكَ قَطَعْتَ عُنُقَ صَاحِبِكَ قَطَعْتَ عُنُقَ صَاحِبِكَ ‏"‏ ‏.‏ مِرَارًا ‏"‏ إِذَا كَانَ أَحَدُكُمْ مَادِحًا صَاحِبَهُ لاَ مَحَالَةَ فَلْيَقُلْ أَحْسِبُ فُلاَنًا وَاللَّهُ حَسِيبُهُ وَلاَ أُزَكِّي عَلَى اللَّهِ أَحَدًا أَحْسِبُهُ إِنْ كَانَ يَعْلَمُ ذَاكَ كَذَا وَكَذَا ‏"‏ ‏.‏
Reference : Sahih Muslim 3000 a
In-book reference : Book 55, Hadith 83
USC-MSA web (English) reference : Book 42, Hadith 7139
  (deprecated numbering scheme)