No one other than Allah (swt) can change His Decree. The infallible Prophet Muhammad (saws) announced that He fears Allah (swt) and linked this fear to a condition, which is the disobedience of Allah. However, since he is a Messenger who is infallible, he will never disobey Allah (swt), and thus, he will not have to be fearful. As such, this verse contains an (if). This verse teaches the ummah of Prophet Muhammad (saws) that the reason to be afraid is disobedience and rebellion against Allah’s Commands.