But Malchizedek, king of Salem, brought out bread and wine; he was a priest of God, the Most High. He blessed him saying, "Blessed is Abram of God, the Most High, Maker of heaven and earth; and blessed be God, the Most High, Who has delivered your foes into your hand"; and he gave him a tenth of everything.Now, it's not so hard to understand the concept of blessing Abram, in the name of God. But Malchizedek also blessed God, and that's a little more complicated. How do you give God a blessing? Can you really give God something he doesn't already have? This is a problem that apparently did bother the Sages, some of which came up with explanations of how he meant different things in each case.
But I think that perhaps it is possible to give God something he doesn't have. In fact, I think God designed us that way.
According to the Rambam (at least I think it was the Rambam), the two tablets are to be understood as being analogs of each other: the first pertaining to the relationship between Man and his Creator; the second pertaining to the relationship between Man and his fellow. Each Commandment deals with the same underlying issue, as applied to each of those categories.
I'm not going to get into that in detail here - perhaps another time. I am going to explain the relationship between the first and sixth, which are pertinent here. First, let's remember that the first Commandment is, "I am the Lord your God..." and the sixth is, "Don't murder."
Now how do these two things relate to each other? The first doesn't even really sound like a Commandment - I mean, what exactly are we being commanded to do? And the sizth is completely baffling... How does one murder God?!
Well, according to Rabbi David Fohrman (and I think he got this from the Rambam too, but I'm not positive about that), you have to consider what the act of murder is: Murder is the process of removing a person from the world. We are not allowed to do that. So what, then is the first Commandment? Well, we're not allowed to remove God from the world either. And how does one remove God from the world? By refusing to recognize Him and His dominion over the Universe.
Now this may seem a little strange to say... I mean, refusing to recognize someone doesn't change the reality? Either God IS or He IS NOT. But the issue isn't really about what IS or IS NOT... it's about what is perceived. One of the primary functions of humanity, and the Jewish People, in particular, is to bring God's Presence into the mundane. "I am the Lord, Your God" is a command to bring God into the world! Don't think that God is out there, God is in here too, and it's our job to make the world aware of that.
And God had that in mind when He created us. He gave us sentience and free-will exactly for this purpose. The one thing that God can't have without us is our appreciation of Him.
I think that's what Malchizedek was trying to demonstrate. We can't give God much... except ourselves, and our blessings.