Why didn’t the Lord just say, “He that keeps My commandments loves me?” (v.21). The Jews were famous for having God’s commandments and not keeping them (Rom.2:17-24), thinking mere possession of them saved them, but this wasn’t so (Rom.2:13). Since the Lord came to minister to these same Jews (Mt.15:24), He said “He that hath My commandments and keepth them…loveth Me.” You had to keep them for the Father to love you (Jo.14:21) enough to save you (Rev.22:14 cf. Gen.3:22). God loves all men, but “specially” those that believe (cf. ITim.4:10).
The Lord planned to manifest Himself to the 12 the same way He was manifested to Israel. He was manifested by His baptism with the Spirit (John 1:31-34), and He planned to manifest Himself to the 12 in their baptism with the Spirit at Pentecost, who was His presence among them.
When Judas (not Iscariot) asked how the Lord would manifest Himself to the 12 but not to the world (14:22 cf. 14:19), that was a good question. Wouldn’t others be able to see them speak in tongues, heal the sick, etc., and other evidence of Christ in them?
The commentaries that don’t rightly divide the word say that Judas was confused, that He didn’t know that the Lord never meant to establish a literal kingdom on earth where He’d be manifest in the hearts of believers but not to the world, so he asked how that would work. We know the Lord did plan to establish a literal kingdom, however, because Daniel 2 described the kingdoms of Media-Persia. Greece and Rome, then said that God would conquer them and set up His kingdom (2:44). If God’s kingdom conquered literal kingdoms, His would have to be a literal kingdom on earth as well.
So how did the Lord plan to manifest Himself to them but not to the world? At Pentecost they kept the His words perfectly (IJo.3:9). That manifested Christ to them, but not to the world, who just assumed they sinned when no one was looking, as the Lord’s brethren did (John 7:5).
But keeping the Lord’s words perfectly meant they also got whatever they asked for in prayer (IJo.3:22). This would also manifest Christ to them, but not to the world, for they wouldn’t abuse this prayer promise, something that would give them away to the world.
For those that love the Lord and keep His commandments the Father and Son would dwell with them (Jo.14:23 cf. Rev.7:14,15; 21:3). Literally? Well, remember, the Lord planned on “restoring” the kingdom to Israel (Acts 1:6), i.e., the kind of literal kingdom they had when God dwelt with them in the wilderness (Ex.25:8; 29:45; Lev.26:11,12 Deut.23:13,14), and in the temple in Jerusalem under Solomon (IKi.8:13).
Not keeping the Lord’s words was serious, for His words were the Father’s words (Jo.14:24).
The Lord was telling them these things at that present time (14:25), but He knew they wouldn’t get it till the Comforter came (v.26). That’s when the children of Israel would receive the adoption and become adult sons (Hos.1:10). That’s when all kids really learn what they were taught when they were kids, when they become adult children!
The Comforter wouldn’t teach them new things, but bring the Lord’s words to their remembrance (14:26 cf. John 2:22; 12:16; Acts 11:15,16). How would that help, if they didn’t understand His words the first time they heard them? Well, with the Word written on their hearts (Jer.31:33), when they heard the words of Christ again they could compare Scripture with the Scripture on their hearts and understand His words (ICor.2:13).
Of course, when it says the Comforter would teach them “all things,” it means all things they’d know to serve Him. He came at Pentecost, which was the beginning of the kingdom that was interrupted by the Mystery. In the kingdom that will still be established on earth after the Rapture and after the Tribulation, men will know everything they need to know to serve Him.