Ahab forgot the word of the Lord

1 Kings 20:31-34
Wearing sackcloth around their waists and ropes around their heads, they went to the king of Isreal and said "Your servant Ben-Hadad says:"please let me live."
The king answered, "Is he still alive? He is my brother."
I will return the cities ay father took from your father," Ben-Hadad offered. "you may set up your own market areas in Damascus, as my father did in Samaria."
Ahab said, "On the basis of a treaty I will set you free." So he made a treaty with him, and let him go.
My father... your father: Meaning ancestor, not actual father.
Why?
Ahab did not asked the Lord and Ahab forgot it is the Lord made him victory. The Lord said 'I will hand over this huge mob of an army to you.'
Ahab saw the profits of the territory and economic benefit from Aram market, so he make treaty with Ben-Hadad and let him go. 
Ahab had not set the Lord in his heart at all!
How?
Do not see the benefit and forget the order of the Lord, God's word is higher than everything. All of the profit are belong to the Lord. When we obey God's word, the Lord will give us more than we expected.