(18) That believed not.--Rather, that disobeyed. Every part of the solemn sentences of the Psalm is applied to the reader's conscience, that the effect of the whole warning may be deepened: the nature of the transgression is thus brought out with the strongest emphasis. Those with whom God was angry had provoked God (Hebrews 3:16), had sinned (Hebrews 3:17), had been disobedient, had refused to believe His word (Hebrews 3:19). The action of the Israelites (Numbers 14) involved at once disobedience to God's command that they should advance to the conquest of the land, and want of faith in the promise which made victory sure.

3:14-19 The saints' privilege is, they are made partakers of Christ, that is, of the Spirit, the nature, graces, righteousness, and life of Christ; they are interested in all Christ is, in all he has done, or will do. The same spirit with which Christians set out in the ways of God, they should maintain unto the end. Perseverance in faith is the best evidence of the sincerity of our faith. Hearing the word often is a means of salvation, yet, if not hearkened to, it will expose more to the Divine wrath. The happiness of being partakers of Christ and his complete salvation, and the fear of God's wrath and eternal misery, should stir us up to persevere in the life of obedient faith. Let us beware of trusting to outward privileges or professions, and pray to be numbered with the true believers who enter heaven, when all others fail because of unbelief. As our obedience follows according to the power of our faith, so our sins and want of care are according to the prevailing of unbelief in us.And to whom sware he that they should not enter into his rest,.... As in Psalm 95:11,

but to them that believed not? the Lord; notwithstanding the signs and wonders he showed among them, they would not be persuaded by Moses and Aaron, by Joshua and Caleb, to be still and quiet, to cease murmuring, and submit to the will of God, and believe in him; they were disobedient, stubborn, and rebellious, and would go up, when they were bid not to go up; for which reason God swore in his wrath that they should not enter into the good land. Unbelief is a source of sin, and cause of judgment, being greatly provoking to God.