1 Peter 1:22-25 (ESV)
Having purified your souls by your obedience to the truth for a sincere brotherly love, love one another earnestly from a pure heart,  since you have been born again, not of perishable seed but of imperishable, through the living and abiding word of God;  for
"All flesh is like grass
and all its glory like the flower of grass.
The grass withers,
and the flower falls,
 but the word of the Lord remains forever."
And this word is the good news that was preached to you.
Again you have this “obedience to the truth” as if the truth, the good news, he is talking about here is a list of rules you are to obey. At least that would be one reading of this translation, and perhaps the more natural reading as it gravitates to our legalist Old Adam. But again it is more, as the context here shows, a listening to the truth, that is by the faith that is formed when you heard the gospel. For we were born from the imperishable spore that is the word of God, and this word is the gospel, the good news, that was preached to you. Good news, is first of all news, rules are not news good or otherwise. But the good news preached to us, is the forgiveness of sins, the ransoming from futile ways through the precious blood of Christ, a lamb without blemish, and this word does not fade like grass, or fail like flowers, as does all our resolution to follow the law of God, to be better people, to refrain from sin. No the good news will remain even when the law of God perishes with this world, being not needed in the world to come, The good news preached to you, the forgiveness of sins, remains forever as the word of the Lord.