The Light - 24:62
The true believers are those who believe in Allah and His Messenger and do not leave him without his permission when he is with him in a social matter. Those who ask your permission are those who believe in Allah and His Messenger. When they ask your permission for some of their affairs, you may give permission to whomever you wish. 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.