The Pleading Woman - 58:4 Whoever cannot find a slave to free should fast for two consecutive months before sexual intercourse. And he who cannot afford it should feed sixty poor people. You must believe in Allah and His messenger. These are the limits set by Allah. The disbelievers are doomed to a painful punishment.
The most important criterion for believing in Allah:
The Cattle/6:82 Those who believe and do not mix their faith with wrongdoing, they deserve security and they have found the truth.

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.

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."