This verse is a concluding statement, going back to the theme of suffering, and in effect assuring the readers of the letter that they are safe under the protection of God. The transitional expression So then may be rendered as “all this means” or “what I am trying to say is…” or “what I am saying is….”
Because it is God’s will is literally “according to God’s will,” for which see 2.15 and 3.17. Peter does not tire in emphasizing that the Christian’s sufferings are part of God’s will for them. Because it is God’s will for them may be rendered as “because this is what God wants for them” or “because this is what God desires that they should experience.”
By their good actions in the Greek is at the end of the verse (literally “in good deeds”). When believers do good in spite of the risks involved, they show that they have come to entrust themselves to God. For the word itself, see 2.15, 20; 3.6, 11; here as there, it refers to good deeds done for others. The phrase by their good actions must in some languages be made a separate clause and be related to the expression should … trust themselves completely to their Creator as a preceding condition, for example, “should do good to others and in this way trust themselves completely to their Creator” or “should be helpful to others and by these good deeds trust themselves completely to their Creator.”
Trust themselves completely is literally “entrust their souls,” with souls standing for the whole man (as in 1.9, 22; 2.11). “Entrust” gives the idea of placing one’s life completely and unreservedly under the protection of another. Trust themselves completely to their Creator may be expressed idiomatically in some languages as “put themselves in the hand of their Creator” or “lean themselves upon their Creator.”
Their Creator is, of course, God; it may be necessary to indicate this fact (for example, Knox “… commend their souls … into his hands; he created them…”). Their Creator may be rendered simply as “the one who made them” or “the one who created them.” However, this might refer in some languages to one’s parents, and therefore it may be necessary to say “to God who created them.”
Who always keeps his promise translates the adjective “faithful” attached to Creator; the idea is that they can entrust themselves to God because he can be trusted, he does not forsake anyone (Die Bibel im heutigen Deutsch), and he is completely reliable (Barclay) and dependable. Who always keeps his promise may be rendered as “he always does what he says he will do.”
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 .