What Is the Meaning of Purity in Christianity ?

When we read the Old Testament, we see that the meaning of purity was simply the washing of the body externally, refraining from eating some kinds of food, avoiding touching certain things, etc. All these rules in the old were for personal hygiene, and they were Jewish traditions. In the Gospel of Mathew, we read that the Scribes and the Pharisees clashed with Jesus over this concept and said to Him, “Why do your disciples transgress the tradition of the elders? For they do not wash their hands when they eat bread” (Mathew 15:2). Jesus answered them with the deep meaning of purity in the New Testament. He gathered the people and told them, “Do you not yet understand that whatever enters the mouth goes into the stomach and is eliminated? But those things which proceed out of the mouth come from the heart, and they defile a man. For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies. These are the things which defile a man, but to eat with unwashed hands does not defile a man” (Mathew 15:10-20).
In these verses, Jesus had laid down a new definition of what is uncleanness and what is purity, which is different from what the Old Testament established for primitive people, that would help them to avoid disease and pollution through cleanliness and external washing.Jesus went into the depth of man’s entity and explained that impurity comes from the heart, the mind, and the thoughts that exude on the body and defile it. It is not consuming certain foods and drinks with unwashed hands that defile the man. Impurity comes from inside, not from outside; a sinful heart, evil thoughts, and lusts of the body are what make man impure.

The main goal of every Christian who has believed in Jesus Christ and has received Him in the Holy Spirit is to become in unity with Him and be more and more like Him each day. To be in unity with Jesus Christ means practically that you must be putting off the old way of life of which sin was in control and conforming one's thoughts and actions to the standard put forth in Scripture. “The power of sin should no longer control the way we live. The Holy Spirit should control the way we live. So don’t live under the control of sin. If you do, you will think about what the spirit wants. ….The mind ruled by the power of sin is at war with God. It doesn’t obey God’s law. It can’t. Those who are under the power of sin can’t please God.” (Romans 8: 6,7,8.)

Some people would say that nobody will ever be perfect or attain sinlessness while still on this earth. That is not true cause Jesus commanded us to be holy as He is holy. So it is a command and not a choice for a believer in Christ. To be holy and pure is the goal for which every Christian strives. The Bible makes a powerful statement regarding this in 1 Thessalonians 4:7,8  "God has called us to be holy, not to live impure lives. Anyone who refuses to live by these rules is not disobeying human rules but is rejecting God, who gives his Holy Spirit to you." And in the first letter of Peter we read “As obedient children, not fashioning yourselves according to the former lusts in your ignorance: But as he which hath called you is holy, so be ye holy in all manner of conversation; Because it is written, Be ye holy; for I am holy.” (1peter14-16).

What we should know that we will never be able to be pure by our works or by our strength, but by our will to be united with the perfect sinless One, our Lord Jesus Christ, the Grace of God given to all mankind.