OK. Just wanted to make that clear:
So you don't actually KNOW how blood washes away sin, let alone that it actually DOES; you only BELIEVE, based on what you've read in the Bible, that it does.
So I guess the next question would be: 'On what basis do you believe that blood contains within it such power?'
It is not about my own intellect or understanding that Im appealing to, it is about Gods truth as He has given in His word. (For English speakers this is the King James Bible, not the new version corruptions.)
I can testify that Jesus Christ has saved me, He dwells within me and I know Him, and His Father and His Holy Spirit. I am cleansed by His blood because Gods word tells me. The born again believer will love the spiritual truths of God and the fact that blood atonement is necessary to cleanse sin. It is how Gods wrath is satisfied and it is Holy. The Godhead dwells within the believer in Christ, by the Holy Spirit they are three but one; distinct but inseparable.
God bears witness to His word, His truths, the Gospel, Who Jesus Christ is; but man resists the conviction of the Holy Ghost, because of pride and self righteousness he will not acknowledge he is a sinner, i.e. not only that youve committed many sins, but that by nature are a sinner and cannot save yourself.
He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God. And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil. For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved. John 3:18-20
If someone responds to Gods conviction of their sinful condition, of the deservingness of hellfire, and of the death, burial and resurrection of Christ He saves them. The death, burial and resurrection are all necessary for mans redemption:
For he is our peace, who hath made both one, and hath broken down the middle wall of partition between us; Having abolished in his flesh the enmity, even the law of commandments contained in ordinances; for to make in himself of twain one new man, so making peace; And that he might reconcile both unto God in one body by the cross, having slain the enmity thereby: Ephesians 2:14-16
For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life. Romans 5:10
But God commendeth his love toward us, in that, while we were yet sinners, Christ died for us. Romans 5:8
For if the dead rise not, then is not Christ raised: And if Christ be not raised, your faith is vain; ye are yet in your sins. 1 Corinthians 15:16-17
But it is the literal physical shed blood of Jesus Christ, God manifest in the flesh that actually cleanses the sin of the believer:
In whom we have redemption through his blood, even the forgiveness of sins: Colossians 1:14
In whom we have redemption through his blood, the forgiveness of sins, according to the riches of his grace; Ephesians 1:7
Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God; Romans 3:25
After the same manner also he took the cup, when he had supped, saying, This cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me. 1 Corinthians 11:25
But now in Christ Jesus ye who sometimes were far off are made nigh by the blood of Christ. Ephesians 2:13
Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood. Acts 20:28
Much more then, being now justified by his blood, we shall be saved from wrath through him. Romans 5:9
And, having made peace through the blood of his cross, by him to reconcile all things unto himself; by him, I say, whether they be things in earth, or things in heaven. Colossians 1:20
But into the second went the high priest alone once every year, not without blood, which he offered for himself, and for the errors of the people: Hebrews 9:7
How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God? Hebrews 9:14
Whereupon neither the first testament was dedicated without blood. Hebrews 9:18
And almost all things are by the law purged with blood; and without shedding of blood is no remission. Hebrews 9:22
Having therefore, brethren, boldness to enter into the holiest by the blood of Jesus, Hebrews 10:19
Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace? Hebrews 10:29
And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel. Hebrews 12:24
For the bodies of those beasts, whose blood is brought into the sanctuary by the high priest for sin, are burned without the camp. Hebrews 13:11
Wherefore Jesus also, that he might sanctify the people with his own blood, suffered without the gate. Hebrews 13:12
Now the God of peace, that brought again from the dead our Lord Jesus, that great shepherd of the sheep, through the blood of the everlasting covenant, Hebrews 13:20
Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers; But with the precious blood of Christ, as of a lamb without blemish and without spot: 1 Peter 1:18-19
But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. 1 John 1:7
And from Jesus Christ, who is the faithful witness, and the first begotten of the dead, and the prince of the kings of the earth. Unto him that loved us, and washed us from our sins in his own blood, Revelation 1:5
And they sung a new song, saying, Thou art worthy to take the book, and to open the seals thereof: for thou wast slain, and hast redeemed us to God by thy blood out of every kindred, and tongue, and people, and nation; Revelation 5:9
And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb. Revelation 7:14
And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death. Revelation 12:11
Gods love is conditional on the person believing on His Son. Although God loved (past tense) the world to die for every persons sin, and He wants all to repent and be saved, He is also righteously angry with and has a just hatred for the wicked (unsaved) for the sake of their sin:
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. John 3:16
God judgeth the righteous, and God is angry with the wicked every day. Psalm 7:11
The foolish shall not stand in thy sight: thou hatest all workers of iniquity. Psalm 5:5
The unsaved will remain under condemnation until, and if, they get saved by believing on Christ and His redemptive work.
Since man is fallen and has a carnal mind at enmity with God it makes sense that an unbeliever who is not spiritually born again and reconciled to God by the blood of Christ, cannot receive His truths or discern that blood atonement is necessary for sin to be cleansed.
Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. Romans 8:7