What is the explaination of verse 4:94?

> O you who have believed, when you go forth [to fight] in the cause of > Allah, investigate; and do not say to one who gives you [a greeting > of] peace, "You are not a believer," aspiring for the goods of worldly > life; for with Allah are many acquisitions. You [yourselves] were like > that before; then Allah conferred His favor [i.e., guidance] upon you, > so investigate. Indeed Allah is ever, of what you do, Aware. (An-Nisa > : 94) What is this verse about? The verse says, "aspiring for the goods of worldly life." This also indicates the intentions of the murderers, so why is the sentence so lenient to them?