Your question, What is the key to truly knowing God? The very same question you’re asking was asked by an apostle. He asked Jesus how will you make yourself known unto us but not unto the rest of the world? Here is what was written. John 14:22 “Judas saith unto him, not Iscariot, Lord, how is it that thou wilt manifest thyself unto us, and not unto the world? Jesus answered and said unto him, If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him.” Abode means home. How is this made possible. Listen again what Jesus said again. John 17:1 “These words spoke Jesus, and lifted up his eyes to heaven, and said, Father, the hour is come; glorify your Son, that your Son also may glorify you: As t You have given him power over all flesh, that he should give eternal life to as many as you have given him. And this is life eternal, that they might know you the only true God, and Jesus Christ, whom you have sent.” It’s all about knowing that the Father and Son has revealed themselves unto you and through you. Eternal life is what Jesus came to give us and it is a personal relationship with him and the Father. How can we know for sure that we know the Lord? It is by his love that he places in our heart that we know him. It is by the comfort of his Holy Spirit that we walk in. It is written as the church grew they walked in the fear of the Lord and the comfort of the Holy Spirit. There is no greater than these two. For the fear the Lord is to hate evil. Proverbs 8:13 “The fear of the LORD is to hate evil: pride, and arrogancy, and the evil way, and the froward mouth, do I hate.” The fear of the Lord separates from these things. The comforts of the Holy Spirit give us strength to endure. Acts 9:31 “Then had the churches rest throughout all Judaea and Galilee and Samaria, and were edified; and walking in the fear of the Lord, and in the comfort of the Holy Ghost,” By these we come to know God dwells in us.