We looked at verse 23 in last week's study but I'm repeating it here because it gives us a running start into today's text. What does our writer mean by "the confession of our hope"(23)? And what is involved in "holding fast" to it "without wavering?"
Then there's the strange way our writer connects his thoughts in these verses. Particularly difficult is abrupt change in tone when we come to verses 26-27 - "For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,  but a fearful expectation of judgment, and a fury of fire that will consume the adversaries."
Where does all of this talk of sin and judgment come from in this text? Verses 24-25 are all about loving and encouraging one another and going faithfully to church. And it's not just that our writer decides to change the subject in 26-27. It's clearly not a brand new topic in our writer's mind. That little word "For...." at the beginning of verse 26 indicates there is some kind of link in the Holy Spirit's mind between what was just said in verses 24-25 and what he is cautioning in verses 26-27.