‘Do not therefore cast not away your boldness, which has great recompense of reward, for you have need of patient endurance, that, having done the will of God, you may receive the promise.'
So he begs them not to be moved by the present uncertainties, Not to toss away their boldness as previously revealed in how they had faced persecution, because now counting it as worthless. For their bold service will bring them great recompense of reward. And in order to do the will of God, as Christ had done before them (Hebrews 10:7-10), and to then receive the promise, they will require the same boldness in order to patiently endure. God's inheritance and God's rewards come through suffering and patient endurance in well-doing (2 Corinthians 1:7; 1 Peter 4:13; Romans 2:7).
‘The Promise.' That is, the good things promised for the future, the coming of Christ (2 Peter 3:4), the heavenly resting place (John 14:2), the coming redemption, the crown of life (James 1:12), the eternal kingdom (James 2:5), eternal life (1 John 2:25; 2 Timothy 1:1), new heavens and a new earth (2 Peter 3:13).