We have been born again (1 Peter 1:3), Peter tells us, to an incorruptible inheritance in heaven (v. 4), which is secure (v. 5) even though the intervening time is difficult (vv. 6-7). Such a salvation as we have is both mysterious and hard to understand, pondered by both the saints of old (v. 10) and angels (v. 12). Yet we have it with more complete understanding and fulfillment than even the prophets ever dreamed possible.
Our rightful response to this knowledge and experience is given in today's verse. We are to "gird up the loins of |our| mind." Just as the flowing robes worn by the men of New Testament times had to be bundled up and tied at the waist to allow for rapid, unencumbered movement, so the Christian is expected to be ready to be on the move, to discipline his or her mind by the renouncing of all sinful and/or confining habits and attitudes.
To do so we must "be sober," be clear-headed, calm, and in control. We must "hope to the end," or more explicitly, "hope to the utmost degree" in our ultimate glorification at the return of Christ. The construction of "hope" implies a command to "fix our hope" on Him, a sure hope, not a wishful hope. This is the "grace that is brought |present tense| to the believer."
Furthermore, we must renounce "the former lusts in |our| ignorance" (v. 14), being "obedient children" of our Father.
It is not enough simply to eliminate sinful patterns from our lives. "But as he which hath called you is holy, so be ye holy" (v. 15).
A mind that is disciplined and purified is ready for action and victory. JDM