Abu Bakr reported that a man was mentioned in the presence of the Prophet, may Allah bless him and grant him peace, and someone praised him. The Prophet, may Allah bless him and grant him peace, said, "Woe to you! You have cut off the head of your companion!" and he repeated that several times. He went on, "If one of you must praise someone, he should say, 'I consider that so-and-so is such-and-such.' Allah is the One who will take account of him if he thinks that he is indeed like that, No one can appropriate Allah's right to attest to someone's character."  

أَنَّ رَجُلاً ذُكِرَ عِنْدَ النَّبِيِّ ﷺ فَأَثْنَى عَلَيْهِ رَجُلٌ خَيْرًا فَقَالَ النَّبِيُّ ﷺ وَيْحَكَ قَطَعْتَ عُنُقَ صَاحِبِكَ يَقُولُهُ مِرَارًا إِنْ كَانَ أَحَدُكُمْ مَادِحًا لاَ مَحَالَةَ فَلْيَقُلْ أَحْسَبُ كَذَا وَكَذَا إِنْ كَانَ يَرَى أَنَّهُ كَذَلِكَ وَحَسِيبُهُ اللَّهُ وَلاَ يُزَكِّي عَلَى اللهِ أَحَدًا  

Abu Musa reported that the Prophet, may Allah bless him and grant him peace, heard a man praise another man and he was using exaggeration in his praise of him. The Prophet, may Allah bless him and grant him peace, said, "You have destroyed - or broken - the man's back."  

سَمِعَ النَّبِيُّ ﷺ رَجُلاً يُثْنِي عَلَى رَجُلٍ وَيُطْرِيهِ فَقَالَ النَّبِيُّ ﷺ أَهْلَكْتُمْ أَوْ قَطَعْتُمْ ظَهْرَ الرَّجُلِ  

Ibrahim at-Taymi reported that his father said, "We were sitting with 'Umar and one man praised another man to his face." He said, "You have wounded the man. May Allah wound you."  

عَنْ أَبِيهِ قَالَ كُنَّا جُلُوسًا عِنْدَ عُمَرَ فَأَثْنَى رَجُلٌ عَلَى رَجُلٍ فِي وَجْهِهِ فَقَالَ عَقَرْتَ الرَّجُلَ عَقَرَكَ اللَّهُ  

Zayd ibn Aslam reported that his father heard 'Umar state, "Praise is slaughter." The transmitter added, "He meant when it is accepted."  

قَالَ مُحَمَّدٌ يَعْنِي إِذَا قَبِلَهَا