The Woman Who Is Examined - 60:12
O Prophet, when the believing women take refuge with you, and they swear by their oaths not to associate anything with Allah, not to steal, not to commit adultery, not to kill their children, not to fabricate a falsehood, and not to oppose you in righteousness, then accept their oaths and ask forgiveness from Allah for them. Allah is Forgiving, Merciful.
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.