3 things, according to O’Brien:
1. Passive dangers
Continually throughout the letter, there are signs that the recipients have developed ‘a certain weariness in pursuing the Christian goal, or making progress along the road of Christian discipleship’.
2. Active dangers
The author warns many times about the seriousness of rebellion and ‘falling away’.
3. External and Outward Pressures
People giving them a hard time for being Christians, bringing suffering through persecution.[P.T.O’Brien, The Letter to the Hebrews. Grand Rapids: Eerdmans, 2010: 9-13.] (citing Ellingworth)
Keller, in some sermons I have listned to, reckons the people who received Hebrews are those who are asking the question: if God is for us, committed to our God, and has redeemed us for all eternity, then why is it so hard living for him right now?