This is one of the biggest plunders of false dispensationalism. To actually believe that the grace of God is limited to the dispensation of grace. How can you go back under Mosaic law, when the Law worketh wrath? All people ever saved, regardless of the dispensation, were saved by Grace through Faith. Abraham believed God, and it wsa counted to him for righteousness. Gen 15. Paul uses the same argument in Gal.
Gal. 3:8 And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed...Gal 3:11 But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith...[Gal 3:16-18 KJV] 16 Now to Abraham and his seed (Christ) were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ. 17 And this I say, [that] the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect. 18 For if the inheritance [be] of the law, [it is] no more of promise: but God gave [it] to Abraham by promise.
[Tit 1:2-3 KJV] 2 In hope of eternal life, which God, that cannot lie, promised before the world began; 3 But hath in due times manifested his word through preaching, which is committed unto me according to the commandment of God our Saviour;...
The actual New Testament is a grace covenant. We as Gentiles are grafted into Israel's olive tree. All the promises and covenants were given to Israel. Rom.9. Those who believe are grafted back into their tree. There is no reason to believe that the Mill. is under the Law? Are the 7 churches under Mosaic Law?
[Rev 22:16 KJV] 16 I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, [and] the bright and morning star.
Rev. starts with 7 ch.. Concludes: with the same 7.