Jamieson, Fausset and Brown on 1 Thessalonians 3:4

4. that we should suffer--Greek, "that we are about (we are sure) to suffer" according to the appointment of God (1Th 3:3).

even as--"even (exactly) as it both came to pass and ye know"; ye know both that it came to pass, and that we foretold it (compare Joh 13:19). The correspondence of the event to the prediction powerfully confirms faith: "Forewarned, forearmed" [Edmunds]. The repetition of "ye know," so frequently, is designed as an argument, that being forewarned of coming affliction, they should be less readily "moved" by it.