The Woman Who Is Examined - 60:1
O you who believe, do not take my enemy as a friend and your enemy as a friend. You show them love while they have denied the truth that has come to you and have driven out the messenger and you (from your country) because you believed in Allah, your Lord. How can you love them secretly if you have gone out on a jihad in My way to win My favor? But I know very well what you conceal and what you reveal. Whoever of you does so has gone astray from the right path.
The most important criterion of belief:
The Cattle/6:82
Those who believe and do not mix their faith with wrongdoing, they deserve security and they have found the truth.
Luqman/31:13
"When Lokman advised his son, he said: "My dear son, do not associate partners with Allah; surely shirk (associating partners with God) is a great wrong."
The Companies/39:65
It has been revealed to you and those before you that if you associate partners, all that you do will be in vain and you will be of the losers.