The Arabic Letter Sad - 38:24
"He said, "He has wronged you by asking to add your sheep to his sheep. Indeed, most of the sharecroppers take away each other´s rights. Except those who believe and do righteous deeds, and how few are they in number!"And David asked forgiveness and bowed down and turned to Us, thinking that We had tested him."
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.