(14) باب النَّهْىِ عَنِ الْمَدْحِ، إِذَا كَانَ فِيهِ إِفْرَاطٌ وَخِيفَ مِنْهُ فِتْنَةٌ عَلَى الْمَمْدُوحِ
'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.
Reference: Sahih Muslim 3000 a
In-book reference: Book 55, Hadith 83
USC-MSA web (English) reference(deprecated numbering scheme): Book 42, Hadith 7139