William Burkitt on Hebrews 10:23

The second duty which the apostle exhorts the Hebrews here unto, is perseverance in the Christian faith and hope, in order to the actual enjoyment of the great reward.

Where observe, 1. The duty itself to hold fast the profession of our faith: not blindly, without due examination; but, having examined the grounds and foundations of our faith, to maintain the profession of it against all tempations and terrors of the world, occasioned by sufferings and persecutions, and against all the cunning arts and insinuations of busy and disputing men, whose design it is to unhinge us from our religion, and make us proselytes to their party and faction: Thus let us hold fast the profession of our faith without wavering.

Observe, 2. The reason enforcing this duty, because he is faithful that has promised. Mark the gradation: We have a promise, even a promise of eternal glory, as the reward of our perseverance. This promise is God's promise, not man's, and the promise of a faithful God, who neither can nor will change his mind; he can as soon change his being as change his word and promise; He is faithful, &c.