All Christians, believing Jews, and those of the Muslim faith believe that the source of all morality is God and what he commands in their respective holy books. They hold the belief that if there were no God, no outside source of morality, that people would do as much evil as they could. But there need be no God for a source of genuine morality and not from outside.
In the Bible morality is dictated by God, whether it is intrinsically good or evil. Some of God's commands in the Old Testament are clearly inhumane and therefore intrinsically immoral, bad, evil. Genocide becomes moral when it is commanded by God. Today, though, all but a few recognize genocide as inherently immoral and bad.
I am an Atheist, what would be called a strong atheist. That just means I'm a confirmed and convinced unbeliever. But that doesn't make me prone to be especially immoral, because I do believe in a source of true morality, societal laws-man made laws. In remote times in the ancient past when man had developed workable intelligence and lived in small clans, the head of the group, or maybe the group collectively, developed some simple rules that attempted to benefit all members of the clan. Over the millennia as larger groups of people began to join together and formed villages, cities, and towns the rules became ever more refined and expanded for the benefit of the greatest possible number of people in a society. It is at it's heart self-interest. One has to see to the well being of everyone else for him to also have well being and happiness.
And being good and helpful to others gives you a psychological pick me up and makes you feel good about yourself.
Some Christians I have talked to have said that were there no God they would have no reason to act morally since there is no promise of reward for morality. And they've said that were there no hell again they would have no reason to act morally, because there will be no retribution, no final judgment. But there is judgment, in this world, handed down by appointed men and women based on the basic law of the greatest benefit to the greatest number of people. When I hear Christians talk like this it makes me suspicious of their true inner character if they are unable to do good simply and only because it is right, and not because of belief that it had been commanded by some god.