Overall meaning : No calamity can ever befall anyone except by Allah’s decree and will. Allah will surely guide the heart of whoever believes in Him and firmly believes that calamities happen only by His decree and will. Allah has full knowledge of all things.
Obey Allah and obey His Messenger, mankind. If you turn away, then bear in mind that Our Messenger’s duty is only to convey the message clearly, with which evidence will be established against you if you then choose unbelief. Allah alone is worthy of worship, and in Allah alone should the faithful put their trust.