Overall meaning : Allah was well pleased with the believers when they pledged their allegiance to you, Muhammad, under the tree at Al-Hudaybiyyah, solemnly promising you to fight against the Quraysh unbelievers and not flee the battlefield. Allah was well aware of the honesty and sincere obedience in their hearts, and so He sent down tranquillity upon them, and rewarded them with a speedy, imminent victory, as well as the rich booty they will take from the Jews of Khaybar, to be exclusively theirs. Allah is the All-Mighty who holds sway over all things, the All-Wise who puts everything in its perfect place.
Allah has promised you, believers, many other spoils that you will take in the future. He has hastened the spoils of Khaybar exclusively for you, who pledged the allegiance, which you will take shortly after returning from Al-Hudaybiyyah, and He has restrained people’s hands from you, such that you have suffered no harm whatsoever at their hands. He has done all this so that such blessings will be a sign and a lesson for the believers of their being assisted by Allah, and so that Allah will guide you along a straight path.
Allah has also promised you, believers, other lands of which you will take possession but are as yet beyond your grasp. Allah has preserved them for you and He will enable you take them after a while. Allah has power over all things. Had the Quraysh unbelievers fought against you in Makkah, they would surely have run away in defeat, and they would have found none to protect or help them against you. Had they fought against you, Allah would certainly have forsaken them, just as He had forsaken their likes among the unbelieving past nations. Victory for the believers and defeat of their unbelievers are part of the immutable and long-established way Allah has set in operation. You will never find any change, Muhammad, in the way Allah has established with regard to His creation.