Therefore gird up the loins of your mind, be sober, and rest your hope fully upon the grace that is to be brought to you at the revelation of Jesus Christ. (1 Peter 1:13 NKJV)
Gird up the loins means to gather your long robes with a belt to prepare for action (for a battle); but this verse is talking about the mind being prepared for action. We’re to be sober which means temperate, restrained, serious, thoughtful, calm, and unruffled.
We can be calm and tranquil because the revelation of Jesus has already occurred! His work is finished! Praise our God!
We’re instructed to rest our hope (confident expectation) upon the grace given to us at the revelation of Jesus, our Savior. We’re so highly blessed to be among those who have received this sacred revelation!
We may rest confidently upon His grace. We may rest, knowing that our salvation was paid for fully by Jesus. There is no work or striving that we need to do, but just to live our lives for Him by the grace that He has already provided.
. . . through whom also we have access by faith into this grace in which we stand, and rejoice in hope of the glory of God. (Rom 5:2)
. . . that having been justified by His grace we should become heirs according to the hope of eternal life. (Tit 3:7)