Expositor's Bible Commentary Commentary Hebrews 7:4

"Now consider how great this man was, unto whom Abraham, the patriarch, gave a tenth out of the chief spoils." — Hebrews 7:4 (ASV)

The author proceeds to bring out the greatness of Melchizedek with an argument that the modern mind may find rather curious but which would have been compelling to his contemporaries. In the ancient world, it was generally recognized that there was an obligation to pay tithes to important religious functionaries. This implies a certain subjection on the part of those paying. So it was significant that Abraham paid to Melchizedek “a tenth of the plunder.” From the spoils of victory an offering would often be made to the gods as a thanksgiving. Abraham gave a tenth of the very best to Melchizedek.