When God speaks, whatever it is comes to pass. Note in Genesis..."and God said" is repeated many times, why, to alert us to the fact that when He says something, it happens. The silliest example would be to say...if God said there was a second Tuesday in the week, we would be changing our calendars.
yes, this is exactly what makes my last statement true, even if it wasn't against his nature to lie, he still could not lie due to the power of his word.