John says there are two results for the one who walks in the light (1:7). First, we will have fellowship with one another. John does not say we have fellowship with God when we walk in the light. Those who are “walking in the light” have fellowship, they live out their relationship with God in a mutually supportive community. Perhaps John has in mind those who have left his community. They are not walking in the light and are therefore not in a state of fellowship with John and his churches.
The second result of walking in the light is that the “blood of Jesus his Son cleanses us from all sin.” Does John say we are saved only after we are walking in the light? (1:7b) Maybe, but it is better to read this in the context of a Jewish writer in the first century.
Purification refers to making someone or something acceptable to God for worship. The verb καθαρίζω can be used in the context of healing a person from a disease which rendered them ceremonially unclean (Lev 14:7; BDAG). In Leviticus, the verb is used for cleansing of food to make it clean (Lev 13:6, 23). The noun καθαρισμός refers to the state of cleanliness required by the Law for worship, so in Mk 1:44 and Luke 5:14 Jesus tells a man healed of leprosy to go to the Temple and do the cleansing ritual required by Moses.
Josephus described the need for purification in Contra Apion:
Josephus, Contra Apion 1.282-283 If any one of their diseases be healed, and he recover his natural constitution again, he appointed them certain purifications, and washings with spring water, and the shaving off all their hair, and enjoins that they shall offer many sacrifices, and those of several kinds, and then at length, to be admitted into the holy city, (283) although it were to be expected that, on the contrary, if he had been under the same calamity, he should have taken care of such persons beforehand, and have had them treated after a kinder manner, as affected with a concern for those that were to be under the like misfortunes with himself.
In the context of Second Temple period Judaism, one needed to be purified before ascending to the Temple Mount to worship. For example, Psalm 24:3-4 asks “Who may ascend the mountain of the Lord?” The answer is the one who has clean hands and pure heart. Although the washing was largely symbolic, it represented the worshiper’s repentance and purification before going up to the Temple courts to worship.
Purification therefore has a nuance of being prepared to worship God in his presence. The blood of Jesus purifies the one who is walking in the light so that they are prepared to enter into fellowship with God in genuine worship. The one who is not walking in the light has not been purified, their worship is not honoring to the Lord. This is exactly what said about Israel’s worship in Amos 5:21-24, The Lord hates Israel’s worship, their songs are just noise and their offerings are unacceptable. God will have no regard for their worship because they do not practice justice and righteousness.
The application of purification in worship is difficult for the contemporary worshiper since we do not participate in a physical ritual before entering into worship. But if we are walking in the light, John assures us we have been purified and we can have genuine fellowship in worship. Is there some way to incorporate purification into contemporary worship? Although I am not advocating for a real washing ritual before going to church, there must be some way a person clears their heart in prayer before they enter into genuine worship.