Overall meaning : Believers, fear Allah by observing what He commands and shunning what He forbids and continue to believe in His Messenger, Muhammad (may Allah bless him and grant him peace). He will grant you two portions of His mercy, provide for you a light by which to be guided in this life and forgive you. Allah is All-Forgiving, All-Merciful.
He will grant you such reward, so that the Jews and Christians may know that they have no power whatsoever over any of Allah’s bounty that He wills to bestow on you, Muslims, and so that they may know that all bounty is in Allah’s hands: He grants it to whomever He wills. Allah’s bounty is limitless.