It is narrated from the Prophet of Islam (PBUH) who said:

The previous tribes and nations fell into extinction because they discriminated in administrating the law. Whenever one of the upper classes committed a crime, they exempted him from punishment, and if a subordinate committed the same crime, he would have been punished. Swear to God, who gave me life; I will not hesitate to administer law on anyone, even if the culprit is one of my relatives [1].

[1] Tabaqat Ibn Sa’ad, Vol. 4, Page 70.

Source: en.shafaqna.com