Genesis 4:3-7
3 So it came about in the course of time that Cain brought an offering to the Lord of the fruit of the ground.
4 Abel, on his part also brought of the firstlings of his flock and of their fat portions. 
And the Lord had regard for Abel and for his offering; 
5 but for Cain and for his offering He had no regard.  So Cain became very angry and his countenance fell. 
6 Then the Lord said to Cain, "Why are you angry? And why has your countenance fallen? 
7 If you do well, will not your countenance be lifted up? 
And if you do not do well, sin is crouching at the door;
and its desire is for you, but you must master it." 

Notice the phrase 'firstlings' from verse four.  Firstlings is a very special term and key to understanding the difference between Cain and Abel's  offerings.  Firstling refers to the very first baby born from a mother.  The nation of Israel was instructed to set aside the firstling of the flock as an offering to the Lord.  Cain and Abel lived thousands of years prior to the establishment of the nation of Israel so it is interesting to see the term firstlings used at this point in time. 

Another interesting item to consider, people did not start eating meat until after the flood.  So what could the flocks be used for except clothing and sacrifice to the Lord.  But how did Abel understand that he needed to come to God with a blood sacrifice?  The answer is the same for you and I.  It is only by the grace of the Living God that we come to an understanding that, as a sinner, I need a blood sacrifice.  Cain came in his own self righteousness which was rejected and caused his countenance to fall. God demands your firstlings.

Genesis 4:7 where God tells Cain that he must master sin is a very interesting concept.  God says that we have a role in this battle against sin.  How do you master sin?  My only answer is that we should walk with God and cling to Him.  In Matthew 15:19-20, Jesus describes the heart of man and the things that defile the man include evil thoughts, murders, adulteries, fornications, thefts, false witness and slanders.  I'm sure this is just a condensed version, but mastering these few items is a full time job for me.  In your battle of trying to master these items from your heart, you will need another weapon which is 1 John 1:9.  If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness. 

Genesis 14:18-20
18 And Melchizedek king of Salem brought out bread and wine; now he was a priest of God Most High. 
19 He blessed him and said, "Blessed be Abram of God Most High, Possessor of heaven and earth;
20 And blessed be God Most High, Who has delivered your enemies into your hand." He gave him a tenth of all. 

Tithe means tenth.  It is, what it is.  Personally, I try to give God more in my tithes than I give the government in my taxes.  Notice all the references in the bible to tithes going to the Levite, the widow and the orphan.  The bible tells us that man will give an account to God for every idol word spoken.  I think that will also apply to every dollar we give in tithes.  Think about it. 

Exodus 13:11-13
11 "Now when the Lord brings you to the land of the Canaanite, as He swore to you and to your fathers, and gives it to you, 
12 you shall devote to the Lord the first offspring of every womb, and the first offspring of every beast that you own; the males belong to the Lord. 
13 But every first offspring of a donkey you shall redeem with a lamb, but if you do not redeem it, then you shall break its neck; and every firstborn of man among your sons you shall redeem. 

Here is the decree regarding the firstling which is the first baby from every womb.  I love how God gets right into the most personal aspect of our human lives.  God talks about babies, wombs, circumcision, virginity, sexual relations, marriage, etc.  Notice in verse 13 how if the animal is not redeemed that it shall die.  What about people?  If people do not accept Jesus as their Lamb of God, they will die. 

Exodus 34:19-20
19 "The first offspring from every womb belongs to Me, and all your male livestock, the first offspring from cattle and sheep. 
20 You shall redeem with a lamb the first offspring from a donkey; and if you do not redeem it, then you shall break its neck.  You shall redeem all the firstborn of your sons.  None shall appear before Me empty-handed. 

God makes a distinction between the male and female in the offerings.  God made Man both male and female.  He loves them both.  God makes a distinction when it comes to form and function.  God will also make a distinction between the whole and the lame.  God loves them both, but again He makes the distinction when it comes to form and function. 

Leviticus 27:26-33
26 'However, a firstborn among animals, which as a firstborn belongs to the Lord, no man may consecrate it; whether ox or sheep, it is the Lord's. 
27 But if it is among the unclean animals, then he shall redeem it according to your valuation and add to it one-fifth of it; and if it is not redeemed, then it shall be sold according to your valuation. 
28 'Nevertheless, anything which a man sets apart to the Lord out of all that he has, of man or animal or of the fields of his own property, shall not be sold or redeemed. 
Anything devoted to destruction is most holy to the Lord. 
29 No one who may have been set apart among men shall be ransomed; he shall surely be put to death. 
30 'Thus all the tithe of the land, of the seed of the land or of the fruit of the tree, is the Lord's; it is holy to the Lord. 
31 If, therefore, a man wishes to redeem part of his tithe, he shall add to it one-fifth of it. 
32 For every tenth part of herd or flock, whatever passes under the rod, the tenth one shall be holy to the Lord. 
33 He is not to be concerned whether it is good or bad, nor shall he exchange it; or if he does exchange it, then both it and its substitute shall become holy.  It shall not be redeemed.'" 

Anything devoted to destruction is most holy to the Lord.  Notice that God says that anything you set apart to the Lord is holy.  Do you dedicate time to God for His service?  If so, that time is holy unto the Lord. 

Numbers 18:17-19
17 But the firstborn of an ox or the firstborn of a sheep or the firstborn of a goat, you shall not redeem; they are holy. You shall sprinkle their blood on the altar and shall offer up their fat in smoke as an offering by fire, for a soothing aroma to the Lord. 
18 Their meat shall be yours; it shall be yours like the breast of a wave offering and like the right thigh. 
19 All the offerings of the holy gifts, which the sons of Israel offer to the Lord, I have given to you and your sons and your daughters with you, as a perpetual allotment.  It is an everlasting covenant of salt before the Lord to you and your descendants with you." 

The firstling of the ox, the sheep and the goat were used as an offering.  These were given as food to the Levites.  Only the burnt offerings were totally consumed in fire.  All the other offerings were given as food. These were happy and festive events.  As you read your bible, notice all the times God eats with His people.  Think about Jesus eating with His disciples or when the Angel of the Lord would eat with people like Abraham or Samson's parents.  Jesus said He is the bread of life.

Numbers 28:26-31
26 'Also on the day of the first fruits, when you present a new grain offering to the Lord in your Feast of Weeks, you shall have a holy convocation; you shall do no laborious work. 
27 You shall offer a burnt offering for a soothing aroma to the Lord: two young bulls, one ram, seven male lambs one year old; 
28 and their grain offering, fine flour mixed with oil: three-tenths of anephah for each bull, two-tenths for the one ram,
29 a tenth for each of the seven lambs; 
30 also one male goat to make atonement for you. 
31 Besides the continual burnt offering and its grain offering, you shall present them with their drink offerings. 
They shall be without defect. 

They shall be without defect.  Are your tithes the firstlings of your earnings?  Are they without defect?  Are they holy unto the Lord? 

Deuteronomy 14:22-23
22 "You shall surely tithe all the produce from what you sow, which comes out of the field every year. 
23 You shall eat in the presence of the Lord your God, at the place where He chooses to establish His name, the tithe of your grain, your new wine, your oil, and the firstborn of your herd and your flock, so that you may learn to fear the Lord your God always. 

Learn to fear the Lord your God ALWAYS.  Paul said that men should work out their salvation with fear and trembling.  Fear of the Lord is respecting Him as the all mighty creator of all things.  Man is made in His image and His image is holy.  His image inside man is what will live on after your body stops breathing air on this earth.  Physical man will die, but the spiritual man will not stop in his existence.  The spiritual man will continue either in fellowship with the Living God by the grace offered by Jesus as the Lamb of God or in the Lake of Fire prepared for the devil and his angels.  Have reverence for the awesome power and unfailing love of our Living God and our adopted Father. 

Verse 23 says that you may learn to fear.  Fear (or reverence) for God is something that you can acquire.  It requires a process of growth over time.  Men do not fear a small ball of clay until they learn that the name of the clay is C4.  Over a period of time working with this clay called C4, men start to understand the power of this material which leads to respect or fear. 

Study your bible and look into the face of the Living God.  You can learn to understand the power and the love of our Creator.  You will learn to respect and fear Him as you consider His awesome power.  Hopefully, you will be blown away by His overwhelming amount of love and grace.  At this point in my short walk with Christ, I do not concern myself any more with why God sends men to hell in judgement.  I am more amazed that He would save a sinner like me.  I look into His face and see the reflection of my heart.  Why does He love me?  Why does He love you?  Because you and I are made in His image.  Thank you Jesus! 

Deuteronomy 15:19-20
19 "You shall consecrate to the Lord your God all the firstborn males that are born of your herd and of your flock; you shall not work with the firstborn of your herd, nor shear the firstborn of your flock. 
20 You and your household shall eat it every year before the Lord your God in the place which the Lord chooses. 

God is in control.  God says you shall do this and do it this way.  Then God says you shall go to where He says and then fellowship together.  Jesus said that if you loved Him that you would keep His commandments.  Jesus commands His people to love the Lord your God and to love each other.  I have always found it interesting how Paul writes the command that men are to love their wives in Ephesians 5:25.  Women are commanded to submit to their husbands, but the command to love is given to the men as Christ gave Himself up for the church. 

Love is a feeling, but love is so much more.  Love is an action.  John 3:16 says God so loved the world that He gave.  Love is an action.  Tithing is an act of love.  Tithing is an act of obedience. Setting aside your firstling is your act of loving obedience to the Living God.