Because thou didst keep (see notes on Revelation 1:3 and Revelation 2:26) the word of my patience, I also will keep thee. This is the Divine lex talionis. "Forgive, and ye shall be forgiven; give, and it shall be given unto you" (Luke 6:37, Luke 6:38); keep, and ye shall be kept.
Compare "I know mine own, and mine own know me" (John 10:14). "The word of my patience" may mean either the gospel, which everywhere teaches patience, or those sayings of Christ in which he specially inculcates this duty (Luke 8:15; Luke 21:19; Matthew 10:22; Matthew 24:13).
In "I also will keep thee" the two pronouns are in emphatic contrast. From the hour of temptation. The phrase, τηρεῖν ἐκ, occurs elsewhere in the New Testament only in John 17:15 (comp. James 1:27, where we have τηρεῖν ἀπό, and 2 Thessalonians 3:3, φυλάσσειν ἀπό).
It is not certain that the common explanation, that ἀπό implies exemption from trial, while ἐκ implies preservation under trial, holds good. "Temptation" ( πειρασμός) generally has no article in the New Testament.
Here it has the article, as if "the temptation" were to be of no ordinary kind. The word does not occur elsewhere in St. John's writings. In order to bring substantive and verb into harmony, the Revised Version renders πειρασμός "trial," the word for "to try" being πειράσαι.
"World" here is not the κόσμος, "the ordered universe" (Revelation 11:15; Revelation 13:8; Revelation 17:8), but the οἰκυμένη, "the inhabited earth" (Revelation 12:9; Revelation 16:14). The phrase, "to dwell upon the earth," κατοικεῖν ἐπὶ τῆς γῆς, is peculiar to the Apocalypse (Revelation 6:10; Revelation 8:13; Revelation 11:10; Revelation 13:8, Revelation 13:14).
"The hour of trial" seems to be that which Christ had foretold should precede his coming, especially the triumph of antichrist. Hence the declaration in the next verse.