Umar on Nepotism: Betrayal of Islam to favor relatives at expense of others

Abdul Malik ibn ‘Umayr reported: Umar ibn al-Khattab, may Allah be pleased with him, said, “Whoever employs a man among his loved ones or relatives, employing him for no other reason besides that, then he has betrayed Allah, His messenger, and the believers.”

Source: Musnad al-Fārūq 740

عن عبد الملك بن عُمَير قال قال عمرُ بن الخطاب رضي الله عنه مَن اسْتعملَ رجلاً لِمَوَدَّة أو لِقَرابَةٍ لا يستعمِلُه إلاَّ لذلك فقد خانَ اللَّهَ وَرَسُولَهُ والمؤمِنينَ

740 مسند الفاروق