4 He that saith, I know him [the Lord Jesus Christ], and keepeth not his commandments, is a liar, and the truth is not in him. 5 But whoso keepeth his word, in him verily is the love of God perfected: hereby know we that we are in him. 1 John 2
Our redemption that we receive when we allow the Lord Jesus to do away with our sins, restores us into fellowship with God, our Creator. This fellowship denotes a knowledge in our heart and soul that is constantly verified in a life of obedience to what he tells us in his word. In John’s writings above, the word “keepeth” means a continual watching, guarding, and observing protectively something that is considered of great value or a treasure.
Taking into account the context of John’s letter, we know he isn’t implying we never sin or have no faults while in our corrupt body that still carries a sin nature. Keeping God’s word, to reveal his love perfected in us, has to do with the idea that we carry out and put into action a genuine desire to habitually observe and obey what he expects of us. The love of God in us is evidenced by our obedience to his word.
People can be well-versed in theology, may claim to be orthodox in their beliefs, a member of a Christian congregation or organization, and vehemently profess to know God, but if their actions show they aren’t truly, habitually, joyfully keeping or guarding God’s word, then they are liars. “They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate,” (Titus 1:16). Their denials and disobedience can be displayed in many forms, such as redefining words and phrases in the Bible to mean what they don’t really mean, in order to justify a sin. This reveals they aren’t really guarding God’s word as a valued treasure. Denials and disobedience can also be displayed when a person habitually and unabashedly has a “potty mouth.” Or if they consult horoscopes instead of prayer and God’s word. Or if they think there’s nothing wrong with sex outside of marriage. Whatever the sin is, it will eventually become obvious in their lives.
So it comes down to examining ourselves and others. Is a Christian confession vindicated by obedience to Divine commands? Is love towards God expressed by a life conformed to his holy will? If so, then we should know that we/they really know the Lord Jesus just like they claim. And that’s something worthy of rejoicing over.