The Great Power of Yom Kippur by Rabbi Benayahu Shmueli, Head of the Yeshiva
Can one say "half pure"? There is no half pure. Half pure is impure! Everything must be completely inside the water, and then the person becomes pure. There is no half, there is no quarter pure. There is no three-quarters pure. Either pure, or not pure! He says: So if that is the case, he says: Today it is "Before Hashem you shall be purified," when a person repents, it is complete purity!

Now we need to do everything possible, so that we may merit now on this day, on Yom Kippur, "Before Whom are you purified, and who purifies you" — do you know what this is? Rabbi Akiva said: "Before Whom are you purified?" What does Rabbi Akiva want to say? Rabbi Akiva wants to say: Know that the forgiveness that we ask for, and the atonement that we ask from the Holy One, Blessed be He, is not just any atonement. This is "Before Hashem you shall be purified" — it is purity. What is purity? It is when a person goes to immerse in a mikveh, he immerses and comes out pure.
Can one say "half pure"? There is no half pure. Half pure is impure! Everything must be completely inside the water, and then the person becomes pure. There is no half, there is no quarter pure. There is no three-quarters pure. Either pure, or not pure! He says: So if that is the case, he says: Today it is "Before Hashem you shall be purified," when a person repents, it is complete purity! It is total cleanliness! The Holy One, Blessed be He, takes the person and polishes him clean from all sins! Such is the power of Yom Kippur.