It can take anywhere from four to twelve hours to soak dried beans in water and rehydrate them, but there's a trick you can use to finish the job in less than two hours.
First, rinse the dried beans with cool water in a colander, picking through and discarding any spoiled beans or stones. Next, pour them into a large pot and boil them.
After a few minutes of boiling, remove the beans from heat and let them sit in the warm water for an hour. Once they're done soaking, you can cook the beans as usual.
If you're not planning to cook the beans further in a chili or other dish, skip the soaking by boiling them on high for 20 minutes, then simmer them to the desired softness.