The Cattle - 6:27
"If you only saw them, when they are stopped by the Fire, saying: "If only we had been turned back so that we had not denied the Verses (revelations and miracles) of our Lord and had been of the believers"!"
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.