The Table Spread - 5:101
Believers, do not ask questions about what you do not like when it is explained to you. If you ask in the light of the Qur´an, they will become clear to you. Allah has not specifically mentioned them. Allah is Forgiving, Mild.
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.