When King Wu was seriously ill, how did Duke Zhou think he could impress the former king?

When King Wu was seriously ill, the ministers were very worried. Taigong and Zhao Gong are going to Wangwen Temple for advice. Duke Zhou believed that only divination could not touch the first king. So the Duke of Zhou set up three altars, facing north, praying to the late king and wishing to serve him instead of the prince of Wu. After praying, the Duke of Zhou divined and got a good omen. It is said that King Wu's condition improved the next day.