God's Promises Are Guaranteed For Eternity.

All the promises of God are yea and amen. For, They are the promises of the God of truth 2 Corinthians 1:20, of him that cannot lie, whose truth as well as mercy endureth for ever.

They are made in Christ Jesus (2 Corinthians 1:20), the Amen, the true and faithful witness; he hath purchased and ratified the covenant of promises, and is the surety of the covenant, Hebrews 7:22.

They are confirmed by the Holy Spirit. He does establish Christians in the faith of the gospel; he has anointed them with his sanctifying grace, which in scripture is often compared to oil; he has sealed them, for their security and confirmation; and he is given as an earnest in their hearts. - Matthew Henry