§ 02 · King James Bible
1 John 2:19
They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
Simple English
They left us and weren't part of us; if they were, they would have stayed. But they left to show they weren't fully with us.
* Work in progress - there may be occasional inaccuracies