10:23

Let us hold firmly . . . without wavering: Opposers were pressuring the Hebrew Christians to reject Christianity and return to observing the Mosaic Law. To avoid wavering or weakening in the face of such pressure, Paul’s readers needed to reject the false teachings of opposers and remain determined to persevere in declaring the Christian hope.​—Compare Heb 3:6.

the public declaration of our hope: First-century Christians publicly declared their hope by expressing their faith before fellow believers as well as by proclaiming the good news about salvation to unbelievers.​—Ps 40:9, 10; Mt 28:19, 20; Ac 1:8; see study note on Ro 10:9.

for the one who promised is faithful: God, who cannot lie, promises everlasting life to those who serve him faithfully. (Ro 6:23; Tit 1:2 and study note; Heb 6:18 and study note) He is fully able to carry out even the most extraordinary of his promises. (Ge 18:13, 14; Ro 4:19-21; Heb 11:11 and study note) And he would consider it unfaithfulness on his part if he were to fail in fulfilling his word. (De 7:9; Ps 146:5, 6) First-century Christians could therefore declare with confidence that God would fulfill all his promises, including the hope of endless life; they knew that such hope was no mere wish or possibility​—it was a certainty.