A few quick observations about these passages that should be in the commentary as well. Melchizedek is one of the most enigmatic characters in the Bible and there is not a for sure answer on who he is. Here is what we can say for sure: he is at the very least a TYPE or ALLUSION to Christ and is meant to be viewed as such, or he is a literal Christophany. It doesn’t matter because we can treat either the same way. Abram gives Melchizedek a tenth or tithe of the spoils. This is before the Mosaic law which tells us this is more than just a legal requisite and is a moral principle God is interested in. BEFORE Abram tithes, he is blessed by the priest king. The moral principle illustrated here is that the tithe is a response or recognition of existing blessing and not just a key to unlock it. Abram doubles down in this passage and even declines the delayed offer from the king of Sodom, “lest anyone say he made Abram rich.” Tithing is more than a response to the gift, it is an acknowledgement of the Giver. The ultimate giver is Christ and we reflect that in our giving as well as in our being. The primary focus of the passage in Hebrews is not necessarily an explanation on tithing, but a declaration that Christ(Melchizedek) is greater than Abraham; the New covenant is greater than the former. The Savior is greater than the law; tithing and giving is now an external expression of an inward submission. the law is now a heart issue, not a letter issue. Matthew is included to complete the NT, OT, Jesus cycle and gives a promising conclusion to the gift idea. Secret giving is associated with a reward from our Father in Heaven. The illustrated detail is how Christ seems to be more interested in HOW you give then IF you give. He assumes we will give, but our attitude will determine the outcome.