“believe” = the tense in the Greek is perfect active indicative. “We have come to believe and still believe.”

“know” = to know; or gain an intimate knowledge of. This same word is used metaphorically of sexual intercourse. The tense is also perfect active indicative and this could read “We have come to know and still know.”

The disciples had come into a faith and intimate knowledge of Jesus and what He had said which had only grown and been reinforced by what they had seen and heard while with Him. The order is important here; you can’t know if you haven’t first believed. They believed and then they knew that He was the Holy One of God.

Believing and knowing is the sure cure against falling away. Do you believe and know Jesus? Or are you riding on the fence, hoping you are saved but not wanting to give yourself fully to Him? Jesus is the One sent from God and when one gets to know Him, one will never leave Him, for there is none that can compare to Him.