If this friend is close enough to help move, then he should be close enough to be completely honest with him.
If it was my friend, I would've kept assuming he was paying until he flat out asked me to pitch in for the bill, in which case I would've said, "Oh, I assumed you were treating because of the move today." Because that would've been the truth, and it's a completely reasonable assumption considering the social convention around friends helping move. If he still insists on splitting, then you have confirmed that your friend is a cheap fuck at best, or takes your friendship for granted at worst. And I would ask him which one he thinks it is