Peter had begun 1 Peter 1:14 with describing his readers as “obedient children” of God, by virtue of their having been “born again” (1 Peter 1:3). Given that reality, God is their “Father.” As is natural in a father/child relationship, children will talk to their father and address him as Father. Peter takes for granted that his readers do the same in relation to God, that is, “if [when, since] you call on him as Father” (= prayer). But since there is an active Father/child relationship between Peter’s readers (exiles of the Dispersion, 1 Peter 1:1) and God, consequences necessarily need to follow.
17 And if you call on him as Father who judges impartially according to each one’s deeds, conduct yourselves with fear throughout the time of your exile,