Albert Barnes on Hebrews 6:12

That ye be not slothful. Indolent; inactive. This was what he was especially desirous of guarding them against. By diligent and strenuous effort only could they secure themselves from the danger of apostasy.

But followers. Imitators--that you may live as they lived.

Of them who through faith and patience. By faith, or confidence in God, and by patience in suffering--referring to those who in times of trial had remained faithful to God, and had been admitted to heaven. In Heb 11 the apostle has given a long list of such persevering and faithful friends of God. See Notes on that chapter.

The promise. The promise of heaven.