3 You are already clean because of the word which I have spoken to you.
The word “clean” may sound familiar. It is the Greek word katharós, which we saw in 2d, meaning to cleanse or make pure, either physically, levitically, or ethically. It carries the concept of something being free from admixture or adhesion of anything that would soil, adulterate, or corrupt. The interesting thing about this verb is it is a tense indicating an action is completed in the past and the subject has already received the action, (Strong’s G2513). From katharos we get the word kathairō, which means to “prune”, or “purge,” to cleanse, properly, from filth and impurity.
Jesus changed the focus a bit from fruit-bearing to talking about the branches by telling the disciples they were already clean through the word he had spoken to them. So, while Jesus spoke earlier of branches that were bearing fruit yet needing to be pruned, or cleansed from filth and impurity, here he is telling his disciples that they were already clean, they did not have any admixture or adhesion of anything that would soil, adulterate, or corrupt.
This concept of being clean is interesting when considering a vineyard. When the vinedresser prunes, he uses shears that have been sanitized. He will even stand in a sanitizing solution to ensure his boots carry no harmful bacteria that might reach the vine. What made the disciples clean was not a sanitizing solution but what they heard Jesus say.
Later, in John 17:8, Jesus said they believed he came from God because of the word he had told them, which word Jesus had received from the Father. Jesus had spoken the truth about himself, his Father, and the Kingdom, and what they believed was pure truth without any falsehoods mixed in. This word had changed the disciples’ belief, as we see with Peter declaring Jesus to be the Messiah and Jesus confirming he only knew this because the Father had revealed it to him.
We all have faith. Faith is simply what we believe, or put our trust in, what we know to be true, not just in our head but in our heart. Our faith, however, can be misplaced, impure. We need our faith to be purified. Scripture teaches us that our faith is cleansed through hearing God speak, since “faith comes by hearing, and hearing by the word of God.” (Rom 10:17)
So how do we get pure faith? Jesus was clear, saying the disciples were clean because of the word he had spoken. When the Holy Spirit speaks to us, it changes us. The Word of God gives us His perspective, which in turn strengthens our faith, or in this analogy, cleanses our faith. This is a key point: The Father speaks truth to us through prayer, reading Scripture, or hearing a talk expounding Scripture. When we hear the word spoken, not just in our physical ears and not even agreeing with a truth intellectually, but when our heart receives what we hear, our beliefs are purified.