The Cow - 2:178
Believers! Equality in killing is enjoined upon you. Free for free, slave for slave, woman for woman. But whoever is forgiven by the relatives of the deceased, then he must do what is fitting and pay the dowry well. This is a mitigation and mercy from your Lord. Then whoever transgresses after that, for him is a painful torment.
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.