Here the obedience of truth Paul is talking about is the gospel of truth.
This argument is presented like this: You have been purified by obeying the gospel of truth so that you can live the sincere born again like which is nothing but showing sincere brotherly love from a sincere and born again heart. This is the positive side of the equation as to what you should do after accepting Christ and becoming a born again Christian.
[22]Seeing ye have purified your souls in obeying the truth through the Spirit unto unfeigned love of the brethren, see that ye love one another with a pure heart fervently:
[23]Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
and all its glory like the flower of the grass;
the grass withers and the flower falls off,
but the word of the Lord endures forever.
And this is the word that was proclaimed to you.
So get rid of all evil and all deceit and hypocrisy and envy and all slander.
And yearn like newborn infants for pure, spiritual milk, so that by it you may grow
up to salvation
The second argument which follows the first can be paraphrased like this
You are born again by the eternal word of God. So get rid of the following
source
The last argument is born from a desire to grow. Yearn for pure spiritual milk 1 Peter 2:3
This is nothing but the basic truth of the Christian faith like repentance,
confession, holiness, prayer, giving, forgiving, brotherly love etc.
In other words hunger and thirst after learning to live these basic spiritual truths in
your life.
