Why does the ruler and creator of the universe care at all about purity? This is a valid question and one that requires much more thought and reason then my little blog may be able to devote but I will do my best to chip away at such a monumental pondering.
We must understand why we are created to be able to answer this question. In the book of Genesis we see the love and care of God both in the creation and in dealing with Adam. We see God walking in the midst of the garden in perfect fellowship with Adam and Eve before the fall and giving them all they desired...all the significance, security and happiness.
God and man lived in harmony until sin entered the world. God made us as free beings because love to be real must be volitional. It wasn't until Adam and Eve rejected God and His perfect will and desired to be a God that the curse of sin entered the world. We desired to rule and reign in our own lives and rejected the relationship that God had ordained. Now, God had every right to leave us in despair and bring harsh judgment to each and every one of us but God loves mercy over judgment.
Joh 1:12 But as many as received Him, to them He gave the right to become children of God, even to those who believe in His name,
From that dire moment in the garden God has been bringing us back into His fold. God does not need our fellowship but desires us to walk with Him. In Jesus Christ the fullness of God is made known to us and to each, by his or her own free will, will either receive Him or reject Him. Under this dispensation of grace we are given ample opportunity to be like Adam and Eve and to walk in the Spirit of God or to walk in the spirit of this world which is a rejection of the love and mercy of God. We will either rule and reign in our own lives to our own peril or we will allow God to rule and reign in us to the glory of Him who loved us and gave Himself for us.
The Christian life is as Paul describes it full of:
Gal 5:22 But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness,
Gal 5:23 gentleness, self-control; against such things there is no law.
It is full of this when we allow the will of God to be made real in our lives. There is no clearer gospel message then what Jesus said in Mark:
Mar 1:15 and saying, "The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel."
Repent - turn from sin, self and Satan's rule in our lives and turn to God.
Believe - Have faith in the message of the Bible and in Jesus Christ for giving Himself for you.
This is not a one time thing but a process of living...when Christ shows you something that is impure, as in the sermon on the mount, the repent from the way you were ruling and reigning and believe God. The word believe and obey are synonyms as we see in John.
Joh 3:36 "He who believes in the Son has eternal life; but he who does not obey the Son will not see life, but the wrath of God abides on him."
Why does God care about purity? Because He cares for us and desires to have fellowship with us. Even if I was a man of unlimited mercy and you continued committing serious heinous crimes against me we cannot have fellowship. Thank God that one day there will be no sin or strife but perfect peace in Him, for those that have received Him and are His children. But to those who reject His mercy and grace they will give an account for the things they have done in God's creation and dispensation of grace.
Rom 2:5 But because of your hardness and unrepentant heart you are storing up wrath for yourself in the day of wrath, when God's righteous judgment is revealed.
Rom 2:6 He will repay each one according to his works:
Rom 2:7 eternal life to those who by patiently doing good seek for glory, honor, and immortality;
Rom 2:8 but wrath and indignation to those who are self-seeking and disobey the truth, but are obeying unrighteousness;