“And Melchizedek king of Salem brought out bread and wine. (He was priest of God Most High.)

And he blessed him and said, ‘Blessed be Abram by God Most High, Possessor of heaven and earth; and blessed be God Most High, who has delivered your enemies into your hand!’ And Abram gave him a tenth of everything” (Genesis 14:18-20).
“Melchizedek” (meaning “My king of righteousness”), was the king of “Salem” (Shalom – peace) and represents a Christological type. The book of Hebrews (ch.7) refers to him in such a way as to suggest that he is indeed the preincarnate Christ. Whatever his identity, Abram pays a tithe to him as God’s representative. This tithe was not given in response to law (the law hasn’t been given yet), nor request, but was given out of gratitude and recognition of God Most High that had given Abram success. Abram gave it willingly.