I will accept nothing belonging to you

Genesis 14:13-23
Abram with Mamre the Amorite, a brother of Ehcol and Aner, he called out the 318 trained men born in his household and went in pursuit as far as Dan. They defeated Kedorlaomer and recovered all the goods and brought back his relative Lot and his possessions, together with the women and the other people.
Melchizedek king of Salem brought out bread and wine to welcome Abram return. He was priest of God, Most High, and he blessed  Abram. Then Abram gave him a tenth of everything.
Abram said to the king of Sodom, "I have raised my hand to the Lord, and I will accept nothing belonging to you, not even a thread or the thong of a sandal, so that you will never be able to say, 'I made Abram rich.' - to Aber, Eshcol and Mamre, let them have their share."
Melchizedek:This is the only appearance of the rather mysterious king/priest of Salem (probably Jerusalem); the name means 'peace'. Melchizedek's authority( a tenth - the 'tithe' - was God's portion, so Abram treats this man as God's representative), his lack of any named ancestors or descendants (extremely important for any man claiming kingship or priesthood), and his dual role as priest and king, let later writers to see in him a foreshadowing of the Messiah.
Why?
Abram blessed from the Lord, his rich was not from anyone, but from the Lord himself. Same as I am, my rich will be from the Lord, Most Height, not from anyone from on the earth. Take what belongs to me, but let my helper take their shares.Them these friend may have good relationship with me and give them good witness.
How?
All I have was given from the Lord, I believed I will rich because of blessings of my Lord, Most High.