tn The referent of ἐν τούτῳ (en toutō) here is more difficult to determine than most, because while there are both ἵνα (hina) and ὅτι (hoti) clauses following, it is not clear whether or not they are related to the ἐν τούτῳ. There are actually three possibilities for the referent of ἐν τούτῳ in 4:17: (1) it may refer to the ἵνα clause which immediately follows, so that the love of believers is brought to perfection in that they have confidence in the day of judgment. The main problem with this interpretation is that since the day of judgment is still future, it necessitates understanding the second use of the preposition “in” (second ἐν [en]) to mean “about” or “concerning” with reference to the day of judgment in order to make logical sense. (2) The ἐν τούτῳ may refer to the ὅτι clause in 4:17b, meaning “love is perfected with us … in that just as he [Christ] is, so also are we in this world.” This makes logical sense, and there are numerous cases where ἐν τούτῳ is explained by a ὅτι clause that follows. However, according to this understanding the intervening ἵνα clause is awkward, and there is no other instance of the phrase ἐν τούτῳ explained by a following ὅτι clause where a ἵνα clause intervenes between the two in this way. (3) Thus, the third possibility is that ἐν τούτῳ refers to what precedes in 4:16b, and this also would make logical sense: “By this—by our residing in love so that we reside in God and he resides in us—is love brought to perfection with us.” This has the additional advantage of agreeing precisely with what the author has already said in 4:12: “If we love one another, God remains in us and his love is brought to perfection in us.” Thus option (3) is best, with the phrase ἐν τούτῳ referring to what precedes in 4:16b, and the ἵνα clause which follows indicates the result of this perfection of love in believers: In the future day of judgment they will have confidence. The ὅτι clause would then give the reason for such confidence in the day of judgment: because just as Jesus is, so also are believers in this world—they are already currently in relationship with God just as Jesus is.

tn The preposition μετά (meta) means “with” and modifies the verb τετελείωται (teteleiōtai). If the prepositional phrase modified the noun ἡ ἀγάπη which immediately precedes it, it would almost certainly have the Greek article, thus: ἡ ἀγάπη ἡ μεθʼ ἡμῶν (hē agapē hē meth’ hēmōn).

sn To say love is perfected with us means “with regard to our actions in loving our brothers.”

tn Grk “that one” (a reference to Jesus is indicated in the context). Once more the author uses the pronoun ἐκεῖνος (ekeinos) to refer to Jesus Christ, as he did in 2:6; 3:3, 5, 7, and 16. A reference to Christ is confirmed in this context because the author says that “just as he is, so also are we [believers] in this world” and since 3:2 indicated that believers are to be like God in the future (but are not yet), the only one believers can be like already in the present age is Jesus Christ.