I suppose there are a few questions in this topic itself.
1 Does the blood of Christ make believers pure?
2 Why bible ask us to purify ourselves?
3 If Christ's blood have made all believers pure, why does
believers still need to purify themelves?
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I believe Icemoon could have been a better person to answer these
questions. Esp when it involves heavily in OT 'Yom Kippur' - The
Day of Atonement. It has great historical significance unto this
question. Mataphorical application of OT to NT.
1 This question consist of a few components
Holiness of God
Sin of Men
Innocent Sacrifice - Blood (The sacrifical Lamb) Offering
Redemption - restoration - cleansing
The sacrifice was needed for reconcilation of God and men.
There are many implications of Christ being a sin offering for
men.
But the main answer in this topic is, Jesus's death is the great
exchange; for man to be able to restore the relationship they have
with God which was lost in Adam.
Yes, the blood of Christ made(cleanses) believers and render them
pure in the eyes of God, which His warth will cease when He sees
the covering of the Blood of Christ upon men(Believers) - The
covenant of Blood. Eph1:7
OT
Gen
8:20 And Noah builded an altar unto the LORD; and took of every
clean beast, and of every clean fowl, and offered burnt offerings
on the altar.
8:21 And the LORD smelled a sweet savour; and the LORD said in his
heart, I will not again curse the ground any more for man's sake;
for the imagination of man's heart is evil from his youth; neither
will I again smite any more every thing living, as I have
done.
NT
Eph
5:2 And walk in love, as the Messiah also loved us and gave Himself
for us, a sacrificial and fragrant offering to God.
Heb
10:10 By this will, we have been sanctified through the offering of
the body of Jesus Christ once and for all.
10:14 For by one offering He has perfected forever those who are
sanctified.
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2 Like quoted from Gospel of Matthew.
Being Pure is a decision, attitude to embrace with.
Believers have this duty to keep themselves as acceptable sacrifice
till the return of Christ.
There is the need or desire to be pure for the things of God and
believers own life.
It is human's effort to retain blamelessness and
refrain from careless acts which might stumble others or
themselves.
Prov 15:26 The thoughts of the wicked are an abomination to the
LORD: but the words of the pure[02889] are pleasant words.
Strong's Concodance Number: 02889
Definition
pure, clean
clean (ceremonially - of animals)
pure (physically)
pure, clean (morally, ethically)
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Mt 5:8 Blessed are the pure[2513] in heart: for they shall see
God.
Ti 2:22 Flee also youthful lusts: but follow righteousness, faith,
charity, peace, with them that call on the Lord out of a pure[2513]
heart.
Strong's Concordance: 2513
Definition =
1 clean, pure
physically
purified by fire
in a similitude, like a vine cleansed by pruning and so fitted to
bear fruit
2 in a levitical sense
clean, the use of which is not forbidden, imparts no
uncleanness
3 ethically
free from corrupt desire, from sin and guilt
free from every admixture of what is false, sincere genuine
blameless, innocent
unstained with the guilt of anything
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1Ti 5:22
Lay hands suddenly on no man, neither be partaker of other men's
sins: keep thyself pure[53].
Strong's Concordance Number: 53
Definition =
1 exciting reverence, venerable, sacred
2 pure
pure from carnality, chaste, modest
pure from every fault, immaculate
clean
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3 God's covenant is seal through believer's
confession onto Jesus Christ is Lord and Savior. His warth will not
befall upon upon those who were cleansed through covenant.
Believers are to keep their end of the covenant by living right and
keeping themselves as godly testimonies before God and men.
Epistle of 1 and 2 Thessalonians have direct instructions of
Christian duties. To be read in context.
1 Thessalonians 4:7
For God hath not called us unto uncleanness, but unto
holiness.
Lastly,
Whatever you may lack, Ask. You'll be given.
Cheers