John Calvin on Hebrews 10:35

35. Cast not away, therefore, etc. He shows what especially makes us strong to persevere, even the retaining of confidence; for when that is lost, we lose the recompense set before us. It hence appears that confidence is the foundation of a godly and holy life. By mentioning reward, he diminishes nothing from the gratuitous promise of Salvation; for the faithful know that their labor is not vain in the Lord in such a way that they still rest on God’s mercy alone. But it has been often stated elsewhere how reward is not incompatible with the gratuitous imputation of righteousness.

Hebrews Chapter 10:36-39

36. For ye have need of patience, that, after ye have done the will of God, ye might receive the promise.

36. Patientiae enim opus habetis, ut quum voluntatem Dei feceritis obtineatis promissionem.

37. For yet a little while, and he that shall come will come, and will not tarry.

37. Adhuc enim pusillum temporis, quando qui venturus est veniet et non tardabit.

38. Now the just shall live by faith: but if any man draw back, my soul shall have no pleasure in him.

38. Justus autem ex fide vivet, et si subductus fuerit non oblectabitur anima mea in eo.

39. But we are not of them who draw back unto perdition; but of them that believe to the saving of the soul.

39. Nos autem non sumus subductionis in perditionem, sed fidei in acquisitionem animae.