A salvation that is eternal in scope, personal in application, and expresses the character of God.
It is not wonder the Scriptures describe it as great.
Sinclair Ferguson wonders how a salvation that embraces the past, present, and future could ever be taken for granted:
So it is in the Gospel. God has a plan. It has been called the covenant of redemption, or the covenant of peace (pactum salutis). Theologians as great as Thomas Boston and Jonathan Edwards have disagreed as to whether the plan should properly be described as a covenant at all. But the debates over nomenclature are incidental to the thing itself.
The triune God had a plan, involving the mutual commitment of Father, Son and Spirit to save a people. About this the reformed theologians speak with one voice.
Before all time; prior to all worlds; when there was nothing “outside of” God himself; when the Father, Son and Spirit found eternal, absolute and unimaginable blessing, pleasure and joy in their holy triunity — it was their agreed purpose to create a world which would fall, and in unison — but at infinitely great cost — to bring you (if you are a believer) grace and salvation. This deeper grace from before the dawn of time — pictured in the rituals, the leaders and the experiences of the Old Testament saints (cf. Heb. 11:39–12:3) — is now ours. These are the dimensions of what the author of Hebrews calls “such a great salvation” (Heb. 2:3). Our salvation depends on God’s covenant, rooted in eternity in the plan of the Trinity, foreshadowed in the Mosaic covenant, fulfilled in Christ, enduring forever. No wonder Hebrews calls it “great.”
You considered your salvation to be “great” early in your Christian life didn’t you? Do you still think about it that way today?
From Ligonier blog.