Col 2:16 Therefore let no one pass judgment on you in questions of food and drink, or with regard to a festival or a new moon or a Sabbath. ESV
Col 2:17 All such things are only a shadow of things in the future; the reality is Christ.   GOOD NEWS BIBLE
The teaching about monetary tithing for Christians has been discredited through the revealing of the reality of Jesus Christ because the tithes and offerings of the old covenant law of Moses were only shadows of the reality of Jesus Christ. Instead, there now are teachings that claim their authority for collecting monetary tithes from Christians because Abram gave tithes to Melchizedek, king of Salem.  These teachers claim that since Abram's tithe was before the old covenant was instituted, that it means God demands that monetary tithes must be given to them.
Gen 14:17 After his return from the defeat of Chedorlaomer and the kings who were with him, the king of Sodom went out to meet him at the Valley of Shaveh (that is, the King's Valley). Gen 14:18 And Melchizedek king of Salem brought out bread and wine. (He was priest of God Most High.) Gen 14:19 And he blessed him and said, "Blessed be Abram by God Most High, Possessor of heaven and earth; Gen 14:20 and blessed be God Most High, who has delivered your enemies into your hand!" And Abram gave him a tenth of everything. ESV

These teachers claim that because Abraham is the father of faith and that he gave a tithe to the king of Salem, it means God requires monetary tithes from Christians. They say they are not teaching about the tithes from the law of Moses since the tithes of Abram in the book of Genesis were before the old covenant law of Moses was given. However, the tithe that Abram gave was only from the spoils of war and not from his personal possessions, and there is no record of Abraham paying tithes of his personal possessions. This was a customary traditional law during the time in which Abram lived. After returning from victory in battle it was the custom to give a tithe of spoils to the regional king-priest, and this was what Abram did when he gave a tithe of the spoils of the battle to the king-priest Melchizedek.  The context of Hebrews 7 is not for the purpose of instructing Christians to tithe monetarily, but it is about the supremacy of Christ's priesthood compared to that of the levitical priesthood.  Hebrews 7 is about the annulling of the old covenant law priesthood of the Levites for the better New Covenant priesthood of Jesus Christ.       
Heb 7:1 For this Melchizedek, king of Salem, priest of the Most High God, met Abraham returning from the slaughter of the kings and blessed him, Heb 7:2 and to him Abraham apportioned a tenth part of everything. He is first, by translation of his name,king of righteousness, and then he is also king of Salem, that is, king of peace. Heb 7:3 He is without father or mother or genealogy, having neither beginning of days nor end of life, but resembling theSon of God he continues a priest forever. Heb 7:4 See how great this man was to whom Abraham the patriarch gave a tenth of the spoils! ESV
Heb 7:17 For it is witnessed of him, "You are a priest forever, after the order of Melchizedek." Heb 7:18 For on the one hand, a former commandment is set aside because of its weakness and uselessness Heb 7:19 (for the law made nothing perfect); but on the other hand, a better hope is introduced, through which we draw near to God. ESV

If we are to follow the Abram's example, which false teachers manipulate by teaching of tithes of the spoil's of war in Genesis 14, then we need to slaughter anyone who attacks our family and take their possessions as the spoils of war. We are to go and give the remaining 90% to the leader of a homosexual community. Abram gave the remaining 90% of the spoils back to the king of Sodom minus that was taken by his allies. Sodom is where we get the word sodomy, and this is a reference to homosexual activity. Abraham's name was still Abram at this time which means exalted father. God changed his name to Abraham which means father of a multitude. God did this through His grace that He extended toward Abraham and not because he gave a tithe to Melchizedek. God brought Jesus through Abraham to establish His eternal New Covenant, but many distort Abraham's story as a means to extract money from Christians with words of deception.  If Abraham ever did works that bought the grace of God as payment, we must set aside Romans 4 and many other New Testament passages.  Righteousness was imputed to Abraham because he trusted that God would bring the Redeemer to save humanity. 
Gen 14:20 and blessed be God Most High, who has delivered your enemies into your hand!" And Abram gave him a tenth of everything. Gen 14:21 And the king of Sodom said to Abram, "Give me the persons, but take the goods for yourself." Gen 14:22 But Abram said to the king of Sodom, "I have lifted my hand to the LORD, God Most High, Possessor of heaven and earth, Gen 14:23 that I would not take a thread or a sandal strap or anything that is yours, lest you should say, 'I have made Abram rich.' Gen 14:24 I will take nothing but what the young men have eaten, and the share of the men who went with me. Let Aner, Eshcol, and Mamre take their share." ESV
Gen 17:2 that I may make my covenant between me and you, and may multiply you greatly." Gen 17:3 Then Abram fell on his face. And God said to him, Gen 17:4 "Behold, my covenant is with you, and you shall be the father of a multitude of nations. Gen 17:5 No longer shall your name be called Abram, but your name shall be Abraham, for I have made you the father of a multitude of nations. ESV
Rom 4:1 What then shall we say was gained by Abraham, our forefather according to the flesh? Rom 4:2 For if Abraham was justified by works, he has something to boast about, but not before God. Rom 4:3 For what does the Scripture say? "Abraham believed God, and it was counted to him as righteousness." Rom 4:4 Now to the one who works, his wages are not counted as a gift but as his due. Rom 4:5 And to the one who does not work but believes in him who justifies the ungodly, his faith is counted as righteousness, ESV

Jacob's promissory tithe that is in Genesis 28 is also used to teach monetary tithing. This is a negative because this scripture shows the character of Jacob. Jacob's name means supplanter, and this is what Jacob was. A person using deceitfulness to get what they want. Jacob just had finished deceiving his father Issac into giving him the blessing of the firstborn son; then he was bargaining with God and making deals with God for protection, but there is no evidence suggesting that Jacob ever fulfilled his vow.  Jacob the supplanter was trying God with his method of deceit, just as he had with his other exchanges that he had with other people.  Jacob's unbelief in God is evident even after God promised to protect him; Jacob began the process of bartering for his safety.  This shows that Jacob was not yet the man of faith that he was destined to be in the grace of God.  Jacob (supplanter) did receive the grace of God when God changed his name to Israel (a prince of God).   
Gen 28:13 And behold, the LORD stood above it and said, "I am the LORD, the God of Abraham your father and the God of Isaac. The land on which you lie I will give to you and to your offspring. Gen 28:14 Your offspring shall be like the dust of the earth, and you shall spread abroad to the west and to the east and to the north and to the south, and in you and your offspring shall all the families of the earth be blessed. Gen 28:15 Behold, I am with you and will keep you wherever you go, and will bring you back to this land. For I will not leave you until I have done what I have promised you." ESV
Gen 28:20 Then Jacob made a vow, saying, "If God will be with me and will keep me in this way that I go, and will give me bread to eat and clothing to wear, Gen 28:21 so that I come again to my father's house in peace, then the LORD shall be my God, Gen 28:22 and this stone, which I have set up for a pillar, shall be God's house. And of all that you give me I will give a full tenth to you." ESV 
Gen 32:27 And he said to him, "What is your name?" And he said, "Jacob." Gen 32:28 Then he said, "Your name shall no longer be called Jacob, but Israel, for you have striven with God and with men, and have prevailed." ESV

Tithes: The Modern Circumcision:
The book of Genesis and the first half of Exodus records historical information that was before the old covenant law of Moses was instituted. These books are contained within the Old Testament and are of the five books of Moses, also known as the Torah or the Book of the Law. All of these scriptures are alluding to God’s plan of salvation even before He had created anything, and this is the meaning behind Jesus being called the Lamb that was slain before the foundation of the world. God knew we would be sinners and commit horrible acts against Him and against one another, but He had already determined beforehand that Jesus would come as the redeemer of us. These teachings about tithes turn the grace of God into greedy sensuality, because they twist it as a means to gain financial profit. Those who teach tithing are guilty of the same sin as the Judaizers in Galatians, because the false teaching concerning tithes of today is the same method that the Judaizers used concerning the false teaching about circumcision in the time of the New Testament. Let me show you the demonstration; the Judaizers in the New Testament were teaching  the believers in Jesus that they had to be circumcised to be saved, but the Spirit condemned this boast of self-righteousness . Circumcision was a shadow of what God would do for us through Christ; it represented how the Spirit would cut away the hardened heart that we had against God and replace it with a heart wanting to do our Father’s will. The book of Galatians teaches that if you are circumcised as a way of acceptance before God, then you are obligated to keep the whole law. Galatians also warns that if you are circumcised for righteousness then you are severed from Christ and that you have fallen from God’s grace. Circumcision was also given to Abraham before the old covenant law of Moses was enacted, and it was the sign in their flesh of God‘s promised redemption. Circumcision was of such great consequence that God threatened to kill Moses, for he had not circumcised his two sons. This was already after God had ordained and was sending him to Egypt to free the Israelites from slavery, and this was in Exodus chapter 4 before the old covenant law of Moses was instituted. The seventh day (Sabbath) in Genesis 2 was also called a holy day by God before the old covenant law of Moses was ratified. The New Testament teaches us that the Sabbath was a shadow of how we are to rest in the work of Jesus that fashions the new creation that we are in Him. Genesis and the first part of Exodus presents information that was before the old covenant law of Moses was instituted, but both belong in the Torah (the book of the law) since they demonstrate that which could only be revealed about Jesus to us from the Holy Spirit. Those teaching tithing from Genesis are no different than the Judaizers that taught circumcision, and Sabbath keeping to New Covenant Christians during the time of the New Testament.
2Co 3:12 Since we have such a hope, we are very bold, 2Co 3:13 not like Moses, who would put a veil over his face so that the Israelites might not gaze at the outcome of what was being brought to an end. 2Co 3:14 But their minds were hardened. For to this day, when they read the old covenant, that same veil remains unlifted, because only through Christ is it taken away. 2Co 3:15 Yes, to this day whenever Moses is read a veil lies over their hearts. 2Co 3:16 But when one turns to the Lord, the veil is removed. 2Co 3:17 Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. 2Co 3:18 And we all, with unveiled face, beholding the glory of the Lord, are being transformed into the same image from one degree of glory to another. For this comes from the Lord who is the Spirit. ESV