In the Qur'an, two of God's ninety-nine names include "the Judge" and "the Just." Muslims believe that God will judge human beings according to His complete justice on the Day of Judgment based both on their beliefs and actions, taking into account the opportunities and abilities that He gave them.
The process outlined in the Qur'anic verses comprise the setting up of scales and all deeds, good and bad, will be placed on either side and if the scales are heavier in good deeds the person has achieved paradise otherwise hellfire.