When is it God for sure? When it is rational and commonsensical? Sometimes. Since we are made in the image of God who gave us common-sense, he presumably employs it himself.
However, what happens when God tells you to do something mind-blowing and outrageous?
What if you live in a desert, surrounded by sand and barrenness, and God tells you to build a ship? Because a flood is coming! A flood? In a desert?
There are these tests of faith along the Christian way, when God asks us to think outside the box, outside the human box. To do the humanly stupid which will be proved wise.
Passing these tests means that God can trust us with further revelation! And directions!
