Verse 4 For it is impossible, &c. This passage (Hebrews 6:4-6) seems intended to induce those addressed to press forward in their Christian course, according to the injunctions of the Hebrews 6:1-3, by urging the danger and the fatal effects of apostasy, to which those who were remiss in their efforts were specially exposed.--Who were once enlightened; who have once been enlightened.