The little phrase "if so be" (Greek ei per) is used four times in the New Testament, each time setting forth a vital spiritual result established on the basis of a vital spiritual premise. The premise in today's verse is that a new Christian has truly experienced the saving grace of Christ. The result will be that these "newborn babes" will truly "desire the sincere milk of the word" (1 Peter 2:2). The "word" (Greek logikos) is always both pure and reasonable.
Then, "ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you" (Romans 8:9). When a person truly receives Christ, the Holy Spirit indwells his body, and the result is that he will henceforth live in the guidance of the Spirit instead of the flesh.
But this life in the Spirit will necessarily entail suffering for the sake of Christ, and this is the premise that assures our future inheritance and glorification. The indwelling Spirit bears witness that we are "heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together" (Romans 8:17).
Finally, our future resurrection is assured by the certainty of the bodily resurrection of Christ. "We have testified of God," Paul says, "that he raised up Christ: whom he raised not up, if so be that the dead rise not" (1 Corinthians 15:15). Christ's resurrection is proved as well as any historical fact has ever been proved, so the dead surely rise also.
These "if-so-be's" of Scripture, although seemingly expressed in the form of conditions, actually speak great assurances. The true Christian life is one of thirst for the logical words of God, guidance by the indwelling Spirit of God, certainty of future resurrection, and anticipation of a glorious inheritance in Christ. HMM