1 John 5:6

tn This ὅτι (hoti) is best understood (1) as causal. Some have taken it (2) as declarative, giving the content of the Spirit’s testimony: “and the Spirit is the One who testifies that the Spirit is the truth.” This is certainly possible, since a ὅτι clause following the cognate verb μαρτυρέω (marture´ō) often gives the content of the testimony (cf. John 1:34; 3:28; 4:39, 44). But in the Gospel of John the Spirit never bears witness on his own behalf, but always on behalf of Jesus (John 15:26, 16:13). There are, in fact, some instances in the Gospel of John where a ὅτι clause following μαρτυρέω is causal (8:14, 15:27), and that is more likely here: “and the Spirit is the One who testifies, because the Spirit is the truth.”