1 John 3:16 New English Translation

¹⁶We have come to know love by this:^[a] that Jesus^[b] laid down^[c] his life for us; thus we ought to lay down our lives for our fellow Christians.

1 John 3:16 tn Here the phrase ἐν τούτῳ (en toutō) is followed by a ὅτι (hoti) clause which is epexegetical (or explanatory), and thus ἐν τούτῳ refers to what follows.
1 John 3:16 tn Grk “that one.” Context indicates a reference to Jesus. The mention of the sacrificial death in 3:16 (ὑπὲρ ἡμῶν τὴν ψυχὴν αὐτοῦ ἔθηκεν, huper ēmōn tēn psuchēn autou ethēken) points to Jesus as the referent here. (This provides further confirmation that ἐκεῖνος [ekeinos] in 2:6; 3:3, 5, and 7 refers to Jesus.)
1 John 3:16 sn References to the fact that Jesus laid down his life using the verb τίθημι (tithēmi) are unique to the Gospel of John (10:11, 15, 17, 18; 13:37, 38; 15:13) and 1 John (only here). From John’s perspective Jesus’ act in giving up his life sacrificially was a voluntary one; Jesus was always completely in control of the situation surrounding his arrest, trials, and crucifixion (see John 10:18). There is a parallel with 1 John 2:6—there, as here, the life of Jesus (during his earthly ministry) becomes the example for believers to follow. This in turn underscores the importance of Jesus’ earthly life and ministry (especially his sacrificial death on the cross), a point of contention between the author and his opponents in 1 John. See 1 John 4:10 for a further parallel.

New English Translation (NET)