Sanctify them by Your truth. Your word is truth.
I read this post at historicalchristian.com today, in which Aimee Cooper posted a news article about her class, Understanding the Catholic Gospel, where she is quoted comparing the catholic gospel to what she calls 'the protestant gospel.' Again, she horribly misrepresents the 'protestant gospel.' She seems deliberately to be using the worst caricatured stereotypes about protestant teaching, which completely misses the richness and simplicity and beauty of the biblical gospel, which bible-believers teach and love.
She states the falsehood that believers are sanctified by the sacrament of the eucharist, instead of by the Holy Spirit working through the truth of God's word as we abide in Christ (See John 15):
“The Catholic Gospel is based on sacramental theology,” explained Cooper. “In the Eucharist, which we believe is the body and blood of Christ … we experience union with God here on earth, which is both physical and spiritual. It’s sacramental theology—it’s infused grace, which is different from Protestant imputed grace, which is only external.”
See my post on 'I Am The Bread of Life' for more on why believing in Jesus is how we 'eat His flesh and drink His blood', not taking the eucharist, which is a symbol and a remembrance of His sacrfice for us.
Aimee says that the Eucharist is what sanctifies catholics:
“He actually lives and grows in us. We are meant to be changed into Christ in our lifetimes,” Cooper said. “It’s what the early Christians believed in the beginning and what the Church has always believed. The Eucharist was the center of life for the early Christians—they protected it, they celebrated it. It’s what changed them and gave them power to witness, to evangelize, to suffer and be martyrs.”
The verse I quoted at the top of this post, John 17:17, gives God's version of the story as Jesus prays to the Father: Sanctify them by Your truth. Your word is truth.
As born-again believers abide in Christ through His word and prayer, we are sanctified within and truly made holy, not just 'dunghills covered in snow' as Aimee quoted from Martn Luther (who was talking about justification, not sanctification; and I don't think I agree with him on this anyway). For born-again christians being justified or made right with God through Christ's imputed righteousness is only the beginning. How are we made holy? See Romans 12:1-2:
1 I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service. 2 And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God.
How are our minds renewed? See Psalm 119:9-11:
9 How can a young man cleanse his way?
By taking heed according to Your word.
10 With my whole heart I have sought You;
Oh, let me not wander from Your commandments!
11 Your word I have hidden in my heart,
That I might not sin against You.
Jesus is the Word and the Bread of Life, and we abide in Him in His word:
4 But He answered and said, “It is written, ‘Man shall not live by bread alone, but by every word that proceeds from the mouth of God.’”