O believers! When you struggle (to fight) in the way of Allah, investigate carefully, and do not say to anyone who offers you a salutation: “You are not a believer” in order to seek worldly gain by this. Allah has abundant spoils for you. Remember that you yourselves were in the same condition before, Allah has conferred His favors on you. Therefore, make a thorough investigation before considering someone an unbeliever. Allah is well aware of all your actions.
Meaning:-
Abundant: existing or available in large quantities; plentiful.
salutation:a gesture or utterance made as a greeting
spoils: goods, advantages, profits, etc. that you get by your actions or because of your position or situation: The spoils of victory/war included mounds of treasure and Armour.