Mark 9:10

And they kept that saying with themselves, questioning one with another what the rising from the dead should mean.

They kept this saying to themselves, questioning what the "rising from the dead" meant.

And they kept the saying, questioning among themselves what the rising again from the dead should mean.

and the thing they kept to themselves, questioning together what the rising out of the dead is.

So they kept this matter to themselves, discussing what it meant to rise from the dead.