tn The ἵνα (hina) clause is best taken as substantival in apposition to ἐν τούτῳ (en toutō) at the beginning of the verse. The Father is glorified when the disciples bring forth abundant fruit. Just as Jesus has done the works which he has seen his Father doing (5:19–29) so also will his disciples.
tc Most mss (א A Ψf13 33 𝔐) read the future indicative γενήσεσθε (genēsesthe; perhaps best rendered as “[and show that] you will become”), while some early and good witnesses (𝔓66vid B D L Θ 0250 1 565 al) have the aorist subjunctive γένησθε (genēsthe; “[and show that] you are”). The original reading is difficult to determine because the external evidence is fairly evenly divided. On the basis of the external evidence alone the first reading has some credibility because of א and 33, but it is not enough to overthrow the Alexandrian and Western witnesses for the aorist. Some who accept the future indicative see a consecutive (or resultative) sequence between φέρητε (pherēte) in the ἵνα (hina) clause and γενήσεσθε, so that the disciples’ bearing much fruit results in their becoming disciples. This alleviates the problem of reading a future indicative within a ἵνα clause (a grammatical solecism that is virtually unattested in Attic Greek), although such infrequently occurs in the NT, particularly in the Apocalypse (cf. Gal 2:4; Rev 3:9; 6:4, 11; 8:3; 9:4, 5, 20; 13:12; 14:13; 22:14; even here, however, the Byzantine mss, with א occasionally by their side, almost always change the future indicative to an aorist subjunctive). It seems more likely, however, that the second verb (regardless of whether it is read as aorist or future) is to be understood as coordinate in meaning with the previous verb φέρητε (So M. Zerwick, “Biblical Greek” §342). Thus the two actions are really one and the same: Bearing fruit and being Jesus’ disciple are not two different actions, but a single action. The first is the outward sign or proof of the second—in bearing fruit the disciples show themselves to be disciples indeed (cf. 15:5). Thus the translation followed here is, “that you bear much fruit and show that you are my disciples.” As far as the textual reading is concerned, it appears somewhat preferable to accept the aorist subjunctive reading (γένησθε) on the basis of better external testimony.