When it comes to deciding what’s right and wrong, we only have three choices:  make up moral law as we go, deciding for ourselves and imposing our view on everyone else;  let some other sinners do this for us, delegating our responsibility to identify the correct moral standard, or  look to God to reveal moral law to us, acknowledging His unique right to define good and evil.
Option 3 is our only reasonable choice, and leads us to expect God to either [A] personally reveal moral law to each and every one of us independently, requiring us all to understand and apply moral law in isolation, effectively making each of us a law unto ourselves, such that we’re unable to either verify or validate our own understanding through the insights of others, or to lawfully hold others accountable for breaking moral law, or [B] to provide a formal written document revealing His moral code, one that we can all access, understand and study together, comparing insights and observations as we seek truth in community. Evidently, B is the only rational choice here.
And given that morality is as complex as life itself, nuanced and multi-faceted in ways that take a lifetime to comprehend, we’d expect God to reveal His righteousness within this written Word in multiple ways: (i) through a clearly defined moral code covering all relevant aspects of our lives; (ii) through stories and accounts of how various peoples have kept or broken this moral code in a wide variety of circumstances, and how God has responded to them; and (iii) through recounting the life pattern of one perfect Man, as He obeys this moral code and walks it out before us. And it is no surprise that this is exactly what we find laid out and preserved for us in Scripture.
God has inspired scripture perfectly (Ps 19:7), even giving it divine life (He 4:12), the perfect spiritual weapon, sufficient to fully enable us unto all good works. (2Ti 3:16-17) God is good, and He is faithful.
To attack this holy document, or any part of it, by altering Scripture in any way, is thus to attack humanity itself, and also God’s intent to reveal Himself to us all; God explicitly forbids this. (De 4:2) For anyone to take upon themselves to diminish, alter or add to the written revelation of God is thus a presumption of the highest order, undermining the very foundation of civilization and spiritual life. (Is 8:20) There is no higher treason than this, to deliberately taint the King’s masterpiece, to misrepresent His heart (Ps 11:3), as if one were qualified to sit in judgment of the Almighty, and correct Him.
Those who commit themselves to carrying out this kind of atrocity, in the myriad of ways that it might be wrought, whether adding to (Pr 30:6), corrupting (2Co 2:17), or taking away from God’s Word (Re 22:19), will necessarily both fail (Jn 10:35b), and also answer to the Author of Scripture for trying to corrupt it; He reserves His severest punishments for such depraved souls. (Re 22:18)
To neglect or misuse such a precious gift is likewise inexcusable; we’re to rightly divide the Word (2Ti 2:15), taking the sword of the Spirit (Ep 6:17), hiding it in our heart and meditating in it day and night (Ps 1:1-3), seeking truth as well as we’re able until we see Him as He is. (1Jn 3:2)