The Repentance - 9:111
Allah has purchased the lives and property of the believers for Paradise. They fight and kill and are killed in the Way of Allah. This is His promise in the Torah, the Gospel and the Qur´an. Who better than Allah can fulfill His promise? So rejoice in this exchange. This is the greatest success.
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.