Sahih Muslim | Book 42 | Hadith Number 7140

Narrated by Abd al-Rahman b. Abu Bakra
Abd al-Rahman b. Abu Bakra reported on the authority of his father that a person was mentioned in the presence of Allah's Apostle (may peace be upon him), and a person said: Allah's Messenger, no person is more excellent than he after Allah's Messenger (may peace be upon him). Thereupon Allah's Apostle (may peace be upon him) said: Woe be to thee, you have broken the neck of your friend, and he said this twice. Then Allah's Messenger (may peace be upon him) said: If anyone has to praise his brother at all, he should say: I think him to be so and so, and even on this he should say: I do not consider anyone purer than Allah (considers). This hadith has been transmitted on the authority of Shu'ba with a slight variation of wording.