“Let us hold fast” How do you read this? It reads like a command. However it is not in the imperative mood in Greek, rather it is subjunctive. But there is no first person imperative in Greek. Since this is the case, this hortatory subjunctive has the force of the imperative here. So holding fast is a command what follows is that to which the writer wants the recipients to hold fast.
“the confession of our hope” – one of the central themes of Hebrews is “better.” We have a better high priest, a better sacrifice, a better hope. That confession, which hope is based on the person that provided better, Jesus. The import of this phrase is that we are to hold fast to, cling to the truth of the gospel.
“without wavering” – this emphasizes the notion of holding fast. The sense of holding fast seems to include the notion of intentionality and unwavering, it is a settled decision, firm in both intention and execution. The repetition of one of the core elements of that thought adds strong emphasis to the command to hold fast.
“for” – this structural marker signals reason. The author is substantiating the imperative to hold fast. What follows is the reason, substantiation for what he has commanded.
“He who promised is faithful” – The reason, substantiation for us to hold fast unwavering is presented as the nature and character of the one who provided the better hope in the first place, the Lord. The unchanging nature of the one who promised is again one of the key themes of Hebrews, see Hebrews 13:8 (here @ Bible Gateway), and in fact one of the themes of the New Testament, consider 2 Timothy 2:11 – 13 (here @ Bible Gateway). Since our hope is based on Him and He is unchanging, our hope and our confession and expression of that hope should be, like Him, unchanging, unwavering.
I will stop here for now. Continue to observe Hebrews 10:23 – 25 (here @ Bible Gateway) and compare what you see to what I shared today and for the next few days.