Come near to God and he will come near to you. Wash your hands, you
sinners, and purify your hearts, you double-minded.
James 4:8 (NIV)
Acts 15:9 also spoke about the purification of the heart.
He did not discriminate between us and them, for he purified their
hearts by faith.
Acts 15:9 (NIV)
Both texts used different Greek words for "purify." James 4:8 used ἁγνίσατε (hagnisate) while Acts 15:9 used καθαρίσας (katharisas). The former defines purity in the sense of "set apart" (pure, different from the world since like the Lord)" while the latter defines purity in the sense of "unmixed" (pure, without undesirable elements). The distinction of meaning reveals in what way purity is being held by the writer.
The Impure Heart
Jesus told us that the origin of a person's defilement or impurity is the heart.
“Are you still so dull?” Jesus asked them. 17“Don’t you see that
whatever enters the mouth goes into the stomach and then out of the
body? 18But the things that come out of a person’s mouth come from
the heart, and these defile them. 19For out of the heart come evil
thoughts—murder, adultery, sexual immorality, theft, false testimony,
slander. 20 These are what defile a person; but eating with unwashed
hands does not defile them.”
Matthew 15:16-20 (NIV)
James 4:8 is addressing its readers to make their hearts different from the world's.The object of the imperative is Christians since the choice of word (ἁγνίσατε not καθαρίσας) directs the command to believers (those set-apart people i.e. the saints). The text tries to pinpoint our identity as God's people, that we are not from this world (John 15:19). It is telling us that the way we live our lives should reflect that reality.
A good man brings good things out of the good stored up in his heart,
and an evil man brings evil things out of the evil stored up in his
heart. For the mouth speaks what the heart is full of.
Luke 6:45 (NIV)
Since Christians have "all the fullness of God" (Ephesians 3:19) and "every good gift comes from God" (James 1:17), their hearts should express their being in God's likeness (James 3:9) from the inside out -- both in words and in deeds (James 1:22).
In James 4:8, the readers who were commanded to purify their hearts were double-minded individuals.
Come near to God and he will come near to you. Wash your hands, you
sinners, and purify your hearts, you double-minded.
James 4:8 (NIV)
It is interesting that the Greek word δίψυχος (lit. two-souled, double-minded) is used in both James 1:8 and James 4:8 since in both occurrences of the word, the same thought is expressed in its context. Our hearts should be expectant that God will grant the desires of our heart (James 1:7-8) that are, of course, in line with God's will (James 2:2-3).
The Heart Purifier
Acts 15:9 is telling us about God's actions inside the believer. It speaks of God making the hearts of the gentiles free from any spiritual defect by means of faith.This is talking about salvation. It is pointing to God's work of putting a new heart to those whom he saves (Ezekiel 36:26).Note that Matthew 5:8 used the same Greek word for purify (καθαροὶ) as found in Acts 15:9.It is interesting since both texts were in the context of salvation.
Blessed are the pure in heart, for they will see God.
Matthew 5:8 (NIV)
Only those whose hearts were pure by faith will see God.
In James 4:8, the way believers purify their hearts must also be by faith because Romans 1:17 says that from start to finish the Just shall live by faith.Faith is the starting point wherein the impure heart is made pure and it is also what makes it possible to have a pure heart until the end.