Imam Ahmad recorded a Hadith from `Abdur-Rahman bin Abi Bakrah, from his father who said,
“A man praised another man in the presence of the Prophet. The Messenger of Allah said:
“Woe to you, you have cut off the neck of your friend! Woe to you, you have cut off the neck of your friend!If one of you must praise a friend of his, let him say: ‘I think that so-and-so is this and that; Allah knows best about him and I will never purify anyone before Allah,’ (if he knows his friend to be as he is describing him.)””
Al-Bukhari, Muslim, Abu Dawud and Ibn Majah collected this Hadith.
Imam Ahmad recorded that Hammam bin Al-Harith said,
A man came before `Uthman bin `Affan and praised him. Al-Miqdad bin Al-Aswad started throwing sand in the face of that man, saying, “The Messenger of Allah ordered us to throw sand in their faces when we see those who praise.” Muslim and Abu Dawud also collected this Hadith.