The Companies - 39:10 "Say: "O you who believe, count your Lord. There is beauty for those who do good in the life of this world. Allah´s abode is spacious. Those who persevere in the truth will be rewarded without calculation."
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.