A.T. Robertson Commentary 1 Peter 5:9

"whom withstand stedfast in your faith, knowing that the same sufferings are accomplished in your brethren who are in the world." — 1 Peter 5:9 (ASV)

Whom withstand (ω αντιστητε). Imperative second aorist active (intransitive) of ανθιστημ; same form in Jas 4:7, which see. Dative case of relative (ω). For the imperative in a subordinate clause see verse 12; 2 Thessalonians 3:10; 2 Timothy 4:15; Hebrews 13:7. Cowardice never wins against the devil (2 Timothy 1:7), but only courage.

Steadfast in your faith (στερεο τη πιστε). Locative case πιστε. Στερεος is old adjective for solid like a foundation (2 Timothy 2:19).

The same sufferings (τα αυτα των παθηματων). An unusual construction with the genitive rather than the usual τα αυτα παθηματα, perhaps as Hofmann suggests, "the same tax of sufferings" ("the same things in sufferings"). Probably this is correct and is like Xenophon's phrase in the Memorabilia (IV. 8. 8), τα του γηρως επιτελεισθα (to pay the tax of old age).

Are accomplished (επιτελεισθα). Present (and so process) middle (you are paying) or passive (is paid) infinitive of επιτελεω, old verb, to accomplish (2 Corinthians 7:1).

In your brethren who are in the world (τη εν τω κοσμω υμων αδελφοτητ). Associateinstrumental case αδελφοτητ (in N.T. only here and 2:17, which see) after τα αυτα (like 1 Corinthians 11:5) or dative after επιτελεισθα. Even so ειδοτες (second perfect active participle of οιδα) with an infinitive usually means "knowing how to" (object infinitive) as in Lu 12:56; Php 3:18 rather than "knowing that" (indirect assertion) as taken above.