Grace allows for reasoning

Genesis 19:19 Behold now, thy servant hath found grace in thy sight, and thou hast magnified thy mercy, which thou hast shewed unto me in saving my life; and I cannot escape to the mountain, lest some evil take me, and I die:

The law of moses didn't allow for any reasoning whatsoever. If you are caught red-handed, you are immediately punished. But because grace predated the law, we see here Lot negotiating with the angels on which place he should go. Although the command was issued to leave Sodom and Gomorrah because of the destruction God was about to send on it, it was not going to be worth the escape if Lot fell into another tragedy where he was sent to and die there perhaps by an attack of a snake or wild animals.

He understood the place of pleading his case with God. Please understand that he wasn't pleading to be excused of performing the command, which was sin in itself, but the modus operandi of how the command would be executed. 

I see sometimes Christians struggle with the way things should be done. They feel that things should be done a certain way, and no change is acceptable whatsoever. Lot should be an example that we have the liberty to choose on how to obey an instruction.

But again, this is not for the immature who haven't yet learnt to exercise these liberties. They need to do as told in a particular way before they can invent a new way for doing things. 

One man said, "What is the use of the mind if it cannot be changed?" Choose to obey in grace with flexibility and not rigidity.

Further scriptures 

Isaiah 1:18 Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.