Perhaps another way of saying it is that God defines sin. Something is sin because God says it is. It was perfectly fine for Adam to marry his daughter or granddaughter. It was perfectly fine for Abram to marry his half sister. But the minute God said to Moses you can't marry your half sister it became sin. So whatever God does or says or thinks is automatically and intrinsically not sin. So how could He sin? He can do whatever He wants and it isn't sin.

__________________
Tim Vaughan, 48 years old, member PCA church but currently attending EV Free church. San Luis Obispo County, California.