A.T. Robertson Commentary 1 Peter 1:20

"who was foreknown indeed before the foundation of the world, but was manifested at the end of times for your sake," — 1 Peter 1:20 (ASV)

Who was foreknown indeed (προεγνωσμενου μεν). Perfect passive participle (in genitive singular agreeing with Χριστου) of προγινωσκω, old verb, to know beforehand (Romans 8:29; 2 Peter 3:17). See προγνωσιν θεου in verse 2.

Before the foundation of the world (προ καταβολης κοσμου). This precise curious phrase occurs in Joh 17:24 in the Saviour's mouth of his preincarnate state with the Father as here and in Eph 1:4. We have απο καταβολης κοσμου in Mt 25:34 (κοσμου omitted in Mt 13:35); Luke 11:50; Hebrews 4:3; 9:26; Revelation 13:8; 17:8. Καταβολη (from καταβαλλω) was originally laying the foundation of a house (Hebrews 6:1). The preincarnate Messiah appears in the counsels of God also in 1 Corinthians 2:7; Colossians 1:26f.; Ephesians 1:9f.; 3:9-11; Romans 16:25; 1 Timothy 1:9.

But was manifested (φανερωθεντος δε). First aorist (ingressive) passive participle of φανεροω, referring to the Incarnation in contrast with the preexistence of Christ (cf. John 1:31; 1 John 3:5,8).

At the end of the times (επ' εσχατου των χρονων). Like επ' εσχατου των ημερων (Hebrews 1:2). The plural χρονο, doubtless referring to successive periods in human history until the fullness of the time came (Galatians 4:4).

For your sake (δι' υμας). Proof of God's love, not of their desert or worth (Acts 17:30f.; Hebrews 11:39f.).