Establish – to set-up, lay a foundation, cause to be; the initial act or process necessary to bring about the end.
Stablish – to render something stable; to stabilize, make secure, or to strengthen something which has already been established.
In Romans chapters 1-3, the doctrine is established for the Dispensation of Grace, in Romans 16:25 we see that the Body of Christ is stablished by that doctrine.
To see how the Bible defines itself, look at I Chronicles 16:30 (which is a reference to Psalms 93:1); a future tense reference to Israel’s kingdom following the Dispensation of Grace, ‘stable … it be not moved’, “Fear before him, all the earth: the world also shall be stable, that it be not moved.”
Psalms 93:1 in an accomplished sense, but still prophetic to Israel’s kingdom, ‘… is stablished’, “The LORD reigneth, he is clothed with majesty; the LORD is clothed with strength, wherewith he hath girded himself: the world also is stablished, that it cannot be moved.“
In II Thessalonians 2:2 the Body of Christ in that city is in peril of being “shaken” or destabilized. “That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.”
God’s purpose according to II Thessalonians 2:17 is to stabilize the Body of Christ in the Dispensation of Grace. “Comfort your hearts, and stablish you in every good word and work.”
In the tribulation, Israel will be established in the gospel that is specifically to them in the book of Hebrews, the Gospel of the Kingdom combined with an understanding of Grace. Israel repeatedly thereafter is being stablished, or stabilized, as is seen throughout James 5. Notice also
I Peter 5:10. “But the God of all grace, who hath called us unto his eternal glory by Christ Jesus, after that ye have suffered a while, make you perfect, stablish, strengthen, settle you.”
The “us” in this passage is the Hebrew Little Flock in the Great Tribulation who is established by the Gospel of the Kingdom, which follows the Dispensation of Grace. They are not Jews, nor are they the Body of Christ that was established by the Gospel of Grace in the Dispensation of Grace. Don’t commit dispensational trespass by trying to include yourself as part of the “us”; it isn’t all about you.