Ahimelech pays dearly for David's deception

1 Samuel 21:1-9
David went to Nob, to Ahimelek the priest.
“Why are you alone? Why is no one with you?” David answered Ahimelek the priest, “The king sent me on a mission and said to me, ‘No one is to know anything about the mission I am sending you on.’ As for my men, I have told them to meet me at a certain place.
Now then, what do you have on hand? Give me five loaves of bread, or whatever you can find.”
So the priest gave him the consecrated bread since there was no bread there except the bread of the Presence that had been removed from before the Lord and replaced by hot bread on the day it was taken away. 
The priest replied, “The sword of Goliath the Philistine, whom you killed in the Valley of Elah, is here; it is wrapped in a cloth behind the ephod. If you want it, take it; there is no sword here but that one.”
Ahimelech pays dearly for David's deception.
Why?
There was not any support, the Priest is the only place has sword and bread, And David can take it.
Under such situation, David has to make deception to Ahimelek.
Ahimelek did right to the consecrated bread, follow the rule before the Lord.
Somehow wisdom is needed.
How?
Deception is not allowed before the Lord. We don't know if David says the truth, God will give him another way to save him.