The Apartments - 49:17
"They want to put you under obligation because they have become Muslims (surrendered). Say, "Do not put your Islam on my head. Indeed, Allah will consider you indebted to Him for bringing you to faith, if you are truthful."
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.