The whole thing is worth reading.
Why is there such a thing as risk? The reason there is such a thing as risk is that there is such a thing as ignorance. If there were no ignorance, there would be no risk. Risk is possible because we don't know how things will turn out.
This means that God can take no risks. He knows the outcome of all his choices before they happen. And since he knows the outcome of all his actions before they happen, he plans accordingly. His omniscience rules out the very possibility of taking risks.