Some theists claim that god is needed for morality. They ask, "How can you be moral without God?"
They might as well ask "How can you be moral with God?" Or better yet, "How can you be moral?", or "What is morality?"
I don't claim to have the answers to those questions. Philosophers have been debating that for thousands of years, and have come up with many contradictory answers, so most of them have to have been wrong.
But bringing god into the question doesn't make it any better. If you say that god's commands are good, you run into the Euthyphro dilemma. Does god command what is good because it is good, or is what is good good, because god commands it?
If the answer is the former, then we're back where we started. If god doesn't determine what's good, then what does?
The alternative has some implications that don't agree with what most people would consider morality. For example, god could change what is moral on a whim, and it wouldn't be wrong. After all, if god determines morality, and it said "It's moral for me to change the laws of morality", well, it couldn't be wrong, now could it?
And consider this analogy (adapted from this). Suppose aliens came to Earth, with overwhelming technological powers. It's impossible for us to fight them, they just vaporize our weapons as soon as we try to use them. And they impose on us some rules that seem quite arbitrary. For example, no one is allowed to wear blue shirts on Tuesday. They reward people who follow their rules, and punish people who don't. Further suppose, that after some time, they eventually leave. Which do you think would be the more common reaction to their departure? "But who will stop us from wearing blue shirts on Tuesdays?" or "Thank god those terrible aliens are gone!"
If what is good is determined solely by god, then his commands would appear to us to be arbitrary. We wouldn't consider a command against murder any more important than a command against blue shirts, and we wouldn't be worried that god is needed to give such a command.