Follow divinely inspired instructions without doubt or opposition

This hadith is about following Prophet Muhammad's teachings even if we know them already. In this particular case, it is about a woman who has performed her obligatory circumambulations on the day of sacrifice but then menstruates afterwards. The Prophet Muhammad taught that she must perform one more circumambulation to make up for it. When Umar was asked about this situation he expressed surprise as he knew what answer to give because it was taught by Prophet Muhammad himself. This teaches us to always follow and respect our prophet's teachings no matter how much we think we know them already or how obvious they may seem to us. We should never doubt or oppose his teachings as they are divinely inspired and come from God Himself.