يَسْـَٔلُونَكَ عَنِ ٱلْأَنفَالِ قُلِ ٱلْأَنفَالُ لِلَّهِ وَٱلرَّسُولِ فَٱتَّقُوا۟ ٱللَّهَ وَأَصْلِحُوا۟ ذَاتَ بَيْنِكُمْ
"They ask you about the spoils. Say: the spoils belong to God and to the Messenger. So guard yourselves against God, and set right what is between you."
The sense of the root: a surplus added to what is basic. Nāfila — an act of worship that is not obligatory, one added on top. The root was treated in al-Anbiyāʾ and in al-Isrāʾ (nāfilatan lak).
The choice of the word is worth recording, and I give this as my own reading: what is taken in battle is named not as a return that has been earned but as something that comes in addition. That is: the naming itself carries the answer to the question within it.
The question is about ownership; the answer comes as two commands, and neither of them has to do with ownership:
Dhāta baynikum — "the state of things between you". The construct names the relationship between two parties as though it were an object: something to be set right.
I record this as an observation: the verse does not say how the division is to be made until the forty-first verse. First it takes up the fact that the dispute over the division has damaged the relationship.