So then not only signals the beginning of a new section, but connects this new section to the previous one in terms of condition-result. Ethical conduct, or the Christian life style which Peter is about to describe, is a result of the theological understanding of the Gospel which he has expounded in verses 3-12. So then may be rendered as “as a result of all this” or “because of all that God has done.” It is important to avoid the implication that So then is only a reference to what the angels would like to understand.
Have your minds ready for action is literally “gird up the loins of your mind.” To “gird the loin” was an appropriate metaphor for people in the Middle East at that time. These people normally wore long gowns, and when someone prepared for any strenuous activity, he “girded” his robe, that is, he tied his robe securely (by using a belt, for example), to make sure that his robe would not be in the way. The metaphor therefore came to mean “be ready for action.” The area of readiness in this verse is the mind, and the full meaning of the metaphor is therefore to prepare oneself mentally (compare New International Version “prepare your minds for action”; Biblia Dios Habla Hoy “Think well what you are about to do”; Die Bibel im heutigen Deutsch “Keep that goal in mind with strong determination”). A literal translation (for example, New American Bible, Revised Standard Version) would produce a very unnatural expression without making the meaning clear.
Have your minds ready for action may be somewhat better expressed in some languages as “prepare your minds for action” or “make your minds ready for action” or simply “be ready in your thinking.”
Peter now specifies what he means by the mind being ready for action. Keep alert is literally “being sober.” The word for “sober” denotes primarily abstinence from wine, but in a wider sense living an ascetic life, a life withdrawn from the activities of this world. Used metaphorically, however, the expression means alertness and sobriety both in speech and in conduct (compare New English Bible “perfectly self-controlled”; Moffatt “keep cool”; Biblia Dios Habla Hoy “live a serious life”). Keep alert may be rendered as “keep yourself under control” or figuratively and from a negative viewpoint as “do not let yourself go in every direction.”
It is possible to take completely with keep alert (compare New English Bible, Knox). Most translations, however, take it with what follows, namely, hope. Set your hope is an aorist imperative. In 1.3, hope is associated with Jesus’ resurrection; here it is associated with his second coming. The expression itself implies not the absence, but the presence of hope, and simply defines its object or goal, namely, the blessing which will be given when Jesus Christ is revealed. Blessing is literally “grace,” and most probably refers to the “salvation” which is discussed in verses 3-12, especially verse 10. One can therefore translate “grace” here as “gift of salvation.” Many translations render “grace” here literally, which does not do justice to what it means in this particular context.
It may be difficult to speak of “hoping completely.” One may, however, indicate something of the significance of hope by translating “your one hope should be the blessing….”
It may be necessary to expand somewhat the nominal expression the blessing into a clause, for example, “how God will bless you” or “how God will show his goodness to you.” The following clause which will be given you may then be rendered as “which he will do for you” or “which he will give to you.”
When Jesus Christ is revealed is literally “at the revelation of Jesus Christ,” which is the same expression used in 1.7 (see above).
Quoted with permission from Arichea, Daniel C. and Nida, Eugene A. A Handbook on The First Letter from Peter. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .