The apostle Philip lived, ate, drank, slept, and traveled with Jesus. After three years, Jesus had to conclude that Philip still did not know Him (Jn 14:9).
After three similar years, the apostle Peter admitted this same fact. Jesus stood bound and accused before the Sanhedrin on the night before He died. Peter looked at him from across the courtyard and said: "I do not even know the Man!" (Mt 26:74) While it is true that Peter spoke words of cowardice, it is also important to realize that Peter really didn't know Jesus. He knew Jesus as Teacher, Master, and Miracle-Worker, but Peter did not know Jesus, the Suffering-Servant.
If the apostles didn't know Him, than how can we know Him? "The way we can be sure of our knowledge of Him is to keep His commandments" (1 Jn 2:3). If we tell ourselves, " 'I have known Him,' without keeping His commandments," we are self-deceived (1 Jn 2:4).
We need to know His commandments in order to obey them. Consequently, we need to spend time reading His word and make it our home (Jn 8:31). In the words of St. Jerome: "Ignorance of the Scriptures is ignorance of Christ" (Catechism, 133).
We will one day find ourselves telling Jesus all the ways in which we knew Him (Mt 7:22; Lk 13:26). But if we did not show that we have known Jesus by knowing and keeping His commandments, His assessment of us will be: "I never knew You" (Mt 7:23).