“a tenth of all.” This is the first time in the Bible that a “tenth,” a “tithe” is mentioned. However, it was not the same as the tithe required by the Mosaic Law (Lev. 27:30-32). The tenth “of all” that Abraham gave was a tenth of the spoils of war he was bringing home from the defeat of Chedorlaomer and the kings who were with him (Gen. 14:17). Abraham had fought them close to Damascus in Syria (Gen. 14:15) and was on his way back home close to Hebron (Gen 14:13), which was about 30 miles south of Jerusalem. So to get from Damascus home, Abraham had to pass by Jerusalem (called “Salem” at the time), where Melchizedek was, and as Abraham was passing by Salem, Melchizedek came out and blessed him, and so Abraham, in recognition of the blessing and in the knowledge that Melchizedek was a priest of Yahweh, the Most High God, gave him a tenth of all the spoils of war he had taken. Abraham’s tenth was a one-time offering (it is never again recorded that Abraham gave a tenth—or any amount at all—to anyone else in recognition that they represented Yahweh, so Abraham’s tenth cannot be compared to the regular tithe commanded by the Law that was given every year. It was at the time of the Exodus, about 400 years after Abraham gave his tenth to Melchizedek, that God told Moses to establish the regular tithe.
The regular tithe in the Law was necessary because God established the Tent of Meeting (Tabernacle), which eventually was the Temple, and it needed lots of manpower and sacrifices to maintain it. So God commanded that the Levites could not own any land (Num. 18:20-24; Deut. 10:9-10), and their portion was to be the part of the tithes and offerings given to Yahweh by the other Israelites. Then, to sustain the Levites, God commanded that the other 11 tribes of the Israelites to give a tenth of all they produced. Before the Tent of Meeting and the separation of the Levites, there was no regular tithe. That brings us to today in the Church Age. There are no more Levites, and the Body of Christ is the Temple. In that light, we can see why God changed from no regular tithe before Moses to a regular tithe when the Tent of Meeting and its regulations were established, and then changed back to giving from the heart as each person decided after the Levites and the Temple were made unnecessary by the death of Christ (2 Cor. 9:7). The New Testament epistles encourage people to give to the poor (Rom. 15:26; Gal. 2:10), to the Lord’s people who needed it (1 Cor. 16:1-2; 2 Cor. 8:14), and to those who serve the Lord (1 Cor. 9:6-14; 1 Tim. 5:17-18). God loves a cheerful giver, and will reward people for the gifts and good deeds they do today (2 Cor. 9:6-8).